GITAM DENTAL COLLEGE & HOSPITAL
DEPARTMENT OF
Oral & Maxillofacial Surgery
SEMINAR ON
Salivary gland diseases Presented By: Dr. Satyajit Sahu III MDS Dept. Of Oral & Maxillofacial Surgery
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Introduction The salivary glands, major and minor, comprise a complex anatomic and physiologic organ system producing enzyme, lubrication, mixing agent and immune factors. The salivary glands respond to physical (food and drink) and emotional (flight, exhilaration and exhaustion) stimuli. They may fall prey to a host of pathologic conditions, including infection, calculus, immune disorders, hypertrophy and atrophy, systemic diseases and neoplasms, both benign and malignant. The diseases of salivary glands may be divided into 1. Developmental anomalies 2. Infections
acute chronic systemic
3. Neoplasms
benign malignant
4. Auto-immune 5. Miscellaneous
necrotising sialometaplasia cystic fibrosis mucocele and ranula
Developmental anomalies Aberrant salivary gland An aberrant (ectopic) salivary gland tissue that develops at a site where it is not normally found. This condition is reported as an single anomaly or in combination with other facial anomalies. They are most frequently reported in the cervical region near the parotid gland or the body of the mandible. The latter is found posterior to the 1st molar and often has a communication with a major salivary gland.
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Most aberrant salivary glands in the neck occur in the upper portion in the area of the branchial cleft and bronchial cleft cysts.
Aplasia and hypoplasia Total aplasia of the major salivary glands, though rare, may occur in combination with other congenital anomalies like cleft palate. The major symptom is severe xerostomia. Hypoplasia of parotid glands has been reported in patients with Melkerson-Rosenthal syndrome, which presents as a classical triad of orofacial granulomas, facial paralysis and fissure tongue.
Accessory glands This is a common condition, found in more than half the people. It is usually found superior and anterior to the normal Stensson’s duct orifice.
Diverticuli These are small pouches or outpocketings of the ductal system of one of the major salivary glands, and these lead to repeated episodes of acute parotitis.
Infections of the salivary glands Sialadenitis, infection of salivary gland tissue is a relatively common tissue. It may be classified as (I)
Bacterial and viral a) Mumps (viral parotitis) b) Bacterial parotitis (sialadenitis)
i. Acute
ii. chronic c) Recurrent parotitis of childhood (II)
Obstructive sialadenitis a) Sialolithiasis b) Mucous plugs
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c) Stricture – stenosis d) Foreign body (III) Systemic granulomatous diseases a) Tuberculosis b) Actinomycosis c) Fungal infection d) Uveoparotid fever
Acute bacterial parotitis Acute bacterial parotitis is a disease of the elderly, malnourished, dehydrated, post-operative and chronically ill patient. Dehydration secondary to acute illness or debilitation result in diminished salivary flow and retrograde infection of Stensson’s duct. Antisialogogues, diuretics, antihistamines and tranquillisers also can be the causes. Clinically, the condition is characterised by the sudden onset of firm, erythematous swelling of parotid region and exquisite pain and tenderness. Body temperature rises and purulent discharge may emanate from Stensson’s duct. If untreated, it leads to a markedly toxic and lifethreatening situation. The treatment of bacterial parotitis includes hydration, antimicrobial therapy (semisynthetic penicillins are found to be adequate), and drainage if necessary. Drainage is accomplished by the surgical exposure of the gland and penetration of capsule by blunt probing using a small Kelly clamp.
Chronic bacterial parotitis This may be secondary to an episode of acute parotitis, and is characterised by unilateral or bilateral swelling of the parotid and by a course of intermittent exacerbations and remissions. Parotidectomy is considered to be the definitive therapy.
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Viral parotitis (mumps) Mumps is an acute communicable disease, occurring in epidemics and transmitted by infected salivary secretions and urine. It usually occurs in a child or in an adult who has previously escaped earlier infection. Mumps is characterised by a rapid, painful swelling of one / both parotids 15 – 18 days after initial exposure. Prodromal phase of 1 – 2 days of fever, headache etc. precedes the swelling. Complications include pancreatitis, orchitis and meningitis (due to viremia). Mumps resolves spontaneously in 5 –10 days. Symptomatic treatment for fever and pain are necessary.
Submandibular sialadenitis This is less common than parotid infection, and is mostly due to stones and strictures. The clinical importance is that it may be confused with submandibular space infections of odontogenic origin.
Sialolithiasis Sialoliths are calcified and organic matter that develop in the parenchyma or ducts of the major or minor salivary glands. Biochemically, they appear laminated with layers of organic material covered with concentric shells of calcified matter. The crystalline structure is chiefly hydroxyapatite and contains octacalcium phosphate. The aetiology of a sialolith is varied. Inflammation, local irritants, antisialogogues etc. are thought to play a significant role. Stones are a common etiologic factor for sialadenitis. Mucous plugs, strictures etc. produce a similar clinical picture. About 80 – 90 % occur in the submandibular gland or duct for the following reasons. •
Wharton’s duct contains sharp curves likely to trap mucin plugs or cellular debris
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•
Calcium levels are high in submandibular saliva
•
Dependent position of the gland
5 – 15 % of sialoliths occur in parotid gland and 2 – 5 % in sublingual and minor salivary glands. Clinically, the most common symptom of sialolithiasis is painful intermittent swelling in the area of a major salivary gland, which worsens during eating and resolves after meals. The pain migrates from the backup of saliva behind the stone or plug. Sialoliths of Stenson’s or Wharton’s duct will be palpable if present in the peripheral portion of the duct. The common site of calculus is buccal mucosa and it presents as an asymptomatic well circumscribed, freely movable draining swelling. Diagnosis:
1. Ordinary radiography 2. Sialography 3. CT scan Treatment:
Acute infections secondary to stasis should be treated with antibiotics. Stones in the distal portion of duct can often be removed manually. Deeper stones require surgery. Lithotripsy has been described as a non-invasive method of disintegrating sialoliths.
Miscellaneous infections of salivary glands Tuberculosis Salivary glands may be primarily involved in tuberculosis, or the disease may infect periglandular lymph nodes. The parotid is most commonly affected. The clinical picture is of a firm, non-tender swelling, resembling a tumour. Draining Salivary glands –Diseases and Management
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fistulae may be present. Diagnostic investigation of chronic salivary gland enlargement should include chest radiograph, skin test and acid fast staining of drainage and culture.
Sarcoidosis (Heerfodt’s disease) This is a chronic, systemic, granulomatous inflammation involving salivary glands in 60 % of cases. Uveoparotid fever occurs in 10 % of cases which present a triad of findings – facial palsy, parotid enlargement and uveitis. Treatment is symptomatic care and long term corticosteroid therapy.
Actinomycosis Actinomycosis israelii is a commonplace member of oral flora and may invade the salivary glands. Sialadenitis occurs in as high as 10 percent of cases of orofacial actinomycosis. Long term high dose penicillin therapy is the treatment of choice.
Diagnosis of salivary gland infections A detailed history and physical examination are useful in the diagnosis of salivary gland infections. The patient who reports acute swelling of a salivary gland at meal time may be diagnosed as having an acute ductal obstruction. Children should be questioned carefully for exposure to epidemic mumps in recent pasts. Careful inspection of oral cavity is mandatory to differentiate between a salivary gland swelling and a space infection of dental origin. Physical examination must include gentle palpation of all major salivary glands and bimanual intraoral and extraoral palpation of ducts. Diagnostic roentgenology may be useful. Indications for plain films or sialography are a) detection of strictures, calculi, foreign bodies b) detection of large parenchymal abscesses
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c) estimation of severity of parenchymal damage or residual function
Tumours of salivary glands Tumours of salivary glands constitute a heterogenous group of lesions of great morphologic variations, and this presents difficulties in having a general classification.
Benign tumours Pleomorphic adenoma (mixed tumour) This is the most common of all salivary gland tumours, constituting over 50 % of all the cases of tumours and about 90 % of all benign salivary gland tumours. It is characterised by a morphologic and histologic complexity marked by the presence of a variety of cell types. Numerous theories have been advanced to explain the histogenesis of this tumour, and the current arguments centre around the myoepithelial cell and a reserve cell in the intercalated duct. It is said that the myoepithelial cell is responsible for the morphologic diversity of the tumour, while the intercalated duct reserve cells can differentiate into ductal cells and myoepithelial cells, which can undergo mesenchymal metaplasia to give rise to more different types of cells.
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Clinical features:
The parotid is the most common site of pleomorphic adenoma (90 %). It may occur, however, in any gland and is more common in women and in patients in 4th to 6th decades. The history is that of a small, painless, quiescent nodule which slowly increases in size. It is usually an irregular nodular lesion which is firm in consistency. Pain is not a common symptom. Among the minor glands, the palatal glands are frequently affected. It may cause difficulties in breathing, talking and mastication. Histology:
The tumour is always encapsulated. The diverse histologic pattern is characteristic. Some areas present cuboidal cells arranged in duct-like pattern with an eosinophilic coagulum. In other areas, the tumour cells may assume a stellate, polyhedral or spindle shape. Some may even show chondroid or osseous character. Treatment:
The accepted treatment is surgical excision. The tumour and the involved lobe are removed. Intra-oral lesions may be treated more conservatively by extracapsular excision. Malignant transformation may occur in a long-standing untreated tumour or in a recurrent one.
Monomorphic adenoma WHO classification of monomorphic adenomas subdivides them into 1) adenolymphoma (Warthin’s tumour) 2) oxyphilic adenoma 3) others, which includes tubular, alveolar (trabecular), basal cell and clear cell adenomas.
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Adenolymphoma (Warthin’s tumour) This unusual type of tumour is found almost exclusively in the parotid gland. This exhibits a definite predilection for men and for age groups of 4 th, 5th and 6th decades.
The tumour is generally superficial, lying just beneath the parotid capsule or protruding through it. It usually does not grow more than 3 –4 cm in diameter . it is painless, firm to palpation and is clinically indistinguishable from other benign lesions. Histologically, the tumour consists of two components – epithelial and lymphoid tissue. It is essential an adenoma exhibiting cyst formation, with papillary projections into the cystic spaces and a lymphoid matrix showing germinal centres. The currently accepted theory of histogenesis is that the tumour arises in salivary gland tissue entrapped in paraparotid or intraparotid lymph nodes during embyogenesis. The treatment is surgical excision of the tumour.
Oxyphilic adenoma (oncocytoma / acidophilic adenoma) This is a rare tumour usually occurring in the parotid gland . it is more common in women and in elderly persons. It does not grow to great size and is clinically not different from other benign tumours
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Microscopically, the tumour is characterised by large cells with an eosinophilic cytoplasm and a distinct cell membrane, and which tends to be arranged in narrow rows or cords. These tumour cells resemble the apparently normal cells called ‘oncocytes’, which are usually seen in a great number of locations in the body. The treatment of choice is surgical excision. The tumour does not tend to recur and malignant transformation is uncommon.
Basal cell adenoma This tumour occurs usually in major salivary glands and a majority of patients are over 60 years of age. It presents as a painless slow-growing lesions. Histologically, it has a well-defined connective tissue capsule, and the cells are isomorphic and basaloid in appearance with basaloid round to oval nuclei. The cells bear similarity to the secretory cells of intercalated duct. The basal cell adenoma is treated by excision.
Canalicular adenoma This occurs in intra-oral accessory salivary glands, mainly in the upper lip. Patients are usually over 60 years of age. It presents as a slow-growing, painless, non-fixed nodule of the lip. Histologic presentation is of cords of epithelial cells, arranged in a double row. The canalicular adenoma is treated by simple excision.
Myoepithelioma It occurs in adults and the parotid gland is the commonest site of occurrence. The commonest intra-oral site is the palate. The tumour is composed of Salivary glands –Diseases and Management
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spindle-shaped or plasmacytoid cells or a combination of the two, set in a myxomatous background. Definitive diagnosis lies in ultrastructural identification of myoepithelial calls. The lesion is treated by excision.
Ductal papillomas Papillomas arising from excretory ducts of salivary glands present in three forms. 1) Simple ductal papilloma – an exophytic lesion with a papillary surface and a pedunculated
base.
2) Inverted ductal papilloma – presents as a nodule of the oral mucosa. 3) Sialadenoma papilliferum – exophytic growth of hard palate. All types are treated by excision.
Benign lymphoepithelial lesion This common lesion exhibits both inflammatory and neoplastic character. The lesion is manifested essentially as a unilateral or bilateral engagement of the parotid and / or submandibular glands with mild discomfort, occasional pain and xerostomia. It is considered to be an auto-immune disease in which the salivary gland tissue becomes antigenic. There is often a diffuse, poorly outlined enlargement of the gland rather than the formation of a discrete nodule. Histologically, there is an orderly lymphocytic infiltration of gland tissue, destroying or replacing the acini. The condition has been treated by both surgical excision and radiation. But the latter is not used now in view of the possibility of radiation induced malignancy. Relation to Mikulicz’s disease
The disease originally described by Mikulicz in 1988 was characterised by a symmetric or bilateral chronic, painless enlargement of the lacrimal and salivary glands. Mikulicz’s patient manifested a benign course without lymphatic involvement. Some later workers noticed that certain cases diagnosed as Mikulicz’s Salivary glands –Diseases and Management
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disease often ran a rapidly fatal course. These were later proved to be malignant lymphomas. It is now believed that Mikulicz’s disease and the benign lymphoepithelial lesion are identical in nature.
Malignant tumours Malignant pleomorphic adenoma This term includes those histologically benign tumours which are shown to have metastases resembling the primary lesion, as well as those which clinically resemble benign pleomorphic adenoma but exhibits cytologically malignant changes. There is considerable debate as to whether they arise from an earlier benign lesion or they represent a malignant lesion from the onset.
There is no obvious clinical difference between benign and malignant pleomorphic adenomas, except an occasional fixity to deeper structures and increased incidences of surface ulceration, pain and regional lymph node enlargement in malignant cases. Frequent metastases to lungs, bones, viscera and brain are seen.
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Histologically, the malignant component may overgrow the benign one or may stay localised in discrete locations. Nuclear changes, invasion of connective tissue, focal necrosis etc. are the features used to determine malignancy. The treatment is essentially surgical, and recurrent lesions are managed by combined surgery and radiotherapy.
Adenoid cystic carcinoma This is a form of adenoid carcinoma, which frequently affect intra-oral accessory salivary glands, parotid and submaxillary glands. Clinical manifestations include local pain, facial paralysis (in case of parotid involvement), fixity to deeper structures, local invasion and surface ulceration. Histologically, the tumour is composed of small, deeply staining uniform cells resembling basal cells, arranged in duct-like pattern, the central portion of which contain a mucoid material. spread of tumour cells along the perineural spaces or sheaths is a common feature.
The treatment is chiefly surgical, but it is often coupled with radiation. This tumour usually metastasises only late in its course and hence long-term follow-up is mandatory.
Acinic cell carcinoma This lesion is peculiar in that the cells show acinar cell differentiation instead of the duct-like pattern seen in other tumours. It closely resembles pleomorphic adenoma in gross appearance. It is reported occurring chiefly in the parotid. Acinic cell carcinoma is composed of cells of varying degrees of Salivary glands –Diseases and Management
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differentiation. Well-differentiated cells resemble normal acinar cells. Lymphoid elements are also commonly seen. The treatment is essentially surgical. The recurrence rate is 8 – 59%, which occurs many years after surgery. Long-term follow-up is necessary.
Mucoepidermoid carcinoma This is an unusual type of salivary gland tumour, described as a separate entity in 1945 by Stewart, Foote and Becker. Majority of cases occurred in parotid. Other gland also may be affected. This tumour has a low-grade malignant variety and a high-grade malignant type. The former appears as a slowly enlarging painless mass. Because of the tendency to develop cystic areas, intra-oral lesions resemble mucocoele. The tumour of high-grade malignancy grows rapidly and produce pain and facial nerve paralysis. The mucoepidermoid carcinoma is not encapsulated; it infiltrates into the surrounding tissue and show metastases. Histologically, this is a pleomorphic tumour composed of mucous-secreting cells, epidermoid-type cells and intermediate cells. The treatment is surgical. Recent data has shown favourable response to radiation therapy. Low-grade malignant type can be managed by surgery alone.
Clear cell carcinoma This is a relatively recently recognised lesion, characterised by the presence of peculiar ‘clear cells’ which are thought to arise from intercalated duct cells or myoepithelial cells. This lesion is also found mainly in major glands, especially parotid. Clear cell carcinoma tends to occur in elderly adults and in females. Clinical presentation is not different from other tumours. Histology shows clusters of clear cells surrounded by a thin septum of fibrous connective tissue. The lesion is treated by surgery. It usually shows a relatively favourable prognosis.
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Epidermoid (squamous cell) carcinoma This tumour involves a grave prognosis, since it exhibits infiltrative properties, metastasises readily and recurs readily. It may arise in any salivary gland. It seems to be of ductal origin, since the ducts undergo squamous metaplasia with ease. A combination therapy of surgery and radiotherapy is indicated.
Salivary gland involvement in rheumatic disease A salivary gland swelling, especially of the parotid, can be a manifestation of auto-immune disease. The distinct subsets of auto-immune salivary gland disease are 1) allergic sialadenitis, 2) SjÜgren’s syndrome / myoepithelial sialadenitis and 3) Epithelial cell sialadenitis / granulomatous sialadenitis.
Allergic sialadenitis This is an acute, but rare, condition. Deposition of antigen-antibody complexes within the parenchyma results in glandular swelling. Removal of allergen is curative. The allergens include certain foods and drugs such as phenyl butazone and nitrofurantoin.
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Myoepithelial sialadenitis (Sjögren’s syndrome) This is a condition originally described as a triad consisting of keratoconjunctivitis sicca, xerostomia and rheumatoid arthritis. Some patients present only with dry eyes and dry mouth (primary Sjögren’s syndrome /sicca complex) while others develop other collagen vascular diseases like SLE, polyarteritis nodosa, scleroderma and rheumatoid arthritis (secondary Sjögren’s syndrome). The disease occurs predominantly in women over 40 years of age. The clinical diagnosis requires a combination of two of the classical triad. Dryness of eyes and mouth cause grittiness and pain in eyes, and pain and burning sensation of oral mucosa. Oral candidiasis, rampant caries and fissured tongue are common. Patients often have bilateral parotid involvement. Other glands also may be affected. Mikulicz’s disease is thought to be synonymous with the salivary component of Sjögren’s syndrome. The lesion may have extra-glandular manifestations like lymphomas. Histologically, intense lymphocytic infiltration of salivary glands and proliferation of ductal epithelium are seen. Antiductal antibodies may be present in the serum of the patients. Other factors like the rheumatoid factor and antinuclear antibodies are also common. ESR may rise to 80%. Sialography may be of diagnostic value in Sjögren’s syndrome. It shows a typical ‘cherry-blossom’ (branchless fruit-laden tree) appearance. There is no satisfactory treatment to Sjögren’s syndrome. The patients are treated symptomatically with artificial tears and salivary substitutes.
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Miscellaneous diseases Cystic fibrosis This condition is transmitted as an autosomal recessive trait and is the most common lethal genetic syndrome among white children. The children suffer from chronic pulmonary disease, pancreatic insufficiency and elevated concentration of electrolytes in sweat. Though mucous-secreting glands are more pathologically involved, parotid saliva is also slightly affected. The elevation of calcium and protein levels in the glands results in the turbidity of secreted fluid owing to the formation of calciumprotein complexes.
Necrotising sialometaplasia Necrotising sialometaplasia is a benign inflammatory reaction of salivary gland tissue, which both histologically and clinically mimics malignancy. The most likely cause is local ischaemia, the cause of which is not known though alcohol and tobacco abuse have been implicated by some workers. The condition occurs more commonly in men. Most patients are in 4 th and 5th decades. Most cases occur in palate, but other intra-oral sites have also been noticed. The lesion generally presents as an ulcer. Pain is not common. Swelling may present in some cases. Necrotising sialometaplasia is histologically characterised by ulcerated mucosa, pseudoepitheliomatous hyperplasia of the mucosal epithelium, acinar necrosis and squamous metaplasia of salivary glands. The lesion is essentially self-limiting and heals by secondary intention.
Mucous retention phenomenon (mucocoele) This is generally conceded to be of traumatic origin, and is a common lesion. It may be caused by traumatic severance of a salivary duct, or a chronic partial Salivary glands –Diseases and Management
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obstruction of a salivary duct. Thus mucocoeles may be classified into extravasation type and retention type. The former is more common. The condition occurs more commonly in lower lip. The lesion may lie fairly deep in the tissue or be exceptionally superficial. The superficial lesion is a raised, circumscribed vesicle with a bluish, transparent cast and is less than 10 mm in diameter. The deeper lesion is also a swelling, but the colour and surface appearance are of normal mucosa. The contents usually consists of thick, mucinous material. Histology shows elevation of mucosa, thinning of epithelium, wall made of a lining of compressed fibrous connective tissue and a lumen filled with an eosinophilic coagulum, containing variable cells. The treatment is excision of the lesion along with the removal o f the associated salivary gland acini.
Ranula This is a form of mucocoele which specifically occurs in the floor of the mouth in association with Wharton’s duct or sublingual ducts. The aetiology and pathology are essentially the same as for mucocoele of other glands. The lesion develops as a slowly enlarging painless mass on one side of the floor of the mouth. Since the lesion is deep-seated, overlying mucosa is normal in appearance. If it is superficial, the mucosa will have a translucent bluish colour. Treatment is to unroof the lesion to drain the contents.
Imaging in salivary gland diseases Multiple imaging techniques may be used in the diagnostic evaluation of salivary gland. These range from plain radiographic examination to the most complex magnetic resonance imaging (MRI).
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Plain radiography Plain radiography still serves an important function in the examination of the salivary glands. It is indicated to identify any radio-opaque sialoliths, phleboliths or dystrophic calcification present in the gland or duct. For evaluation of parotid gland, PA view, true lateral and lateral oblique views with the chin extended and mouth open, should be performed. For evaluation of submandibular gland, the lateral view radiograph should be taken with index finger pressing the tongue down. In addition, an intra-oral occlusal view may be helpful. About 80% of salivary calculi can be visualised with plain radiography. They appear as focal calcific densites, most commonly associated with submandibular gland.
Nuclear medicine (radionuclide imaging) The findings of nuclear medicine techniques are less specific than sialography, CT or MRI. But this may be useful as an adjunct to these techniques. Intravenous injection of 10 mCi of Tc-99m pertechnate is performed with gamma camera images obtained every 2 minutes. Abnormalities may be defined as increased, decreased or absent uptake of radionuclide. Increased uptake is seen in sialadenitis and granulomatous diseases and in oncocytoma and Warthin’s tumour. Decreased uptake is seen in ageing, viral infections and most tumours.
Ultrasonography This provides a non-invasive means for examination of the salivary glands, with the exception of the deep lobe of parotid. The differentiation between cystic and solid compartments can easily be made. Fluid-filled structures with no tissue interfaces, such as an abscess or cyst, appear echo-free on ultrasound studies. Solid structures, such as heterogeneous tumour, appear filled with multiple echoes and various shades of grey. Salivary glands –Diseases and Management
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High frequency transducers in the order of 7.5 MHz are used. Sequential images in transverse and longitudinal planes are performed. Ultrasonography may be used in the evaluation of all types of pathology within the salivary glands. In the case of inflammatory lesions, the chronicity of the process determines the sonographic pattern.
Sialography Sialography is the direct radiographic demonstration of the salivary gland and duct system by injection of radio-opaque contrast material into the ductal orifice. The three main indications for the performance of sialography are (i)
sudden acute swelling of a gland possibly secondary to ductal obstruction by a stone or stricture,
(ii)
progressive glandular enlargement or symptoms suggesting recurrent inflammation,
(iii)
palpable salivary gland masses.
Technique:
Prior to canulation of the duct, conventional radiographic examination is indicated to determine the radiographic view. No premedication or local anaesthesia is required for sialography. After placement of cannula in the duct, an oily contrast material such as ethiodol is introduced by either hydrostatic pressure or gentle intermittent manual injection. Contrast injection is performed under fluoroscopic Salivary glands –Diseases and Management
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guidance. The gland should be visualised during ductal filling, acinar filling, evacuation and post-evacuation stages. Findings:
In chronic inflammatory sialadenitis, focal dilatation of peripheral ducts and globular or sacular collections of contrast are noted in an irregular pattern throughout the gland. Delayed contrast evacuation is noted. In auto-immune diseases, punctate or globular collections of contrast material is homogeneously seen throughout the gland, and these do not disappear during evacuation. Sjögren’s syndrome is characterised by a ‘cherry-blossom’ (branchless fruit-laden tree) appearance. In evaluation of calculi, plain radiography is superior to sialography since most calculi are radio-opaque, and the contrast may obscure it. Granulomatous diseases and lymphoma has a similar sialographic appearance. The findings have a progressive nature depending on the course of the disease. Sialography may also be used to evaluate lacerations or haematoma formations. Sialography is contra-indicated in cases of (i)
acute infection and
(ii)
history of allergy to the contrast medium.
Computed tomography (CT) The primary indications of CT evaluation include masses or generalised enlargements of one or more glands, acute inflammatory processes or abscesses. This technique is helpful in diagnosis, treatment planning and in evaluating response to the treatment. Routine CT may be performed with or without intravenous contrast administration. The CT has a 10-fold advantage over conventional radiographs in the detection of calcifications within the glands. Acute and chronic inflammation, benign and malignant tumours and cysts can be visualised. In the case of malignant Salivary glands –Diseases and Management
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tumours, infiltration to surrounding tissues may be seen. Also, facial nerve and other associated structures may be visualised, and this aid in treatment planning.
Magnetic resonance imaging (MRI) The indications for CT and MRI overlap. MRI is the examination of choice for the evaluation of neoplastic lesions. The advantages of MRI include increased soft tissue contrast at the margins of the tumour. The major disadvantages include the high cost, limited availability of facilities and increased technical complexity. MRI examination of salivary glands uses a superconducting magnet with a field-strength of 1.5 T. Routine examination includes slice thickenings of 5 mm or less. The MR appearance of pleomorphic adenoma and Warthin’s tumour is inhomogeneous with low signal intensity compared to the normal gland. In Warthin’s tumour, cystic components are encountered. Fibrosis or calcifications appear as areas of low signal or signal void. Malignant tumours show a lower intensity signal than that of benign tumours. Haemorrhagic spots appear as high intensity images. The use of MRI in salivary gland disease is limited because many diseases show similar patterns. The contra-indications to MRI include pacemakers, ferromagnetic valvular clips and implanted neurostimulation devices.
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Surgical Management of Salivary Gland Diseases With the possible exception of surgical management of retention cysts like mucoceles and ranulas, transoral sialolithotomy is the most frequent operation performed on salivary system. This is a simple operation often but overlooked by the medical practitioner untrained in oral surgery in favour of enucleation of the gland. If the stone is favourably located, its removal through the mouth preserves the gland and hence its function. The submandibular gland can be enucleated without harmful sequelae if the operation is properly accomplished. In most patients with normal salivary secretion in the remaining glands its removal is of no consequence. However parotid gland is of greater concern. Danger to the facial nerve is always present although careful surgery permits removal of this gland with only transient weakness in most instances. Removal of either gland will result in a significant facial deformity. However these factors are most significant if operation is necessary but contraindicate such procedures when conservative methods would suffice. Tumours involving the parotid, submandibular, sublingual or minor salivary glands located in the cheek, lips palate may also warrant their removal in certain instances. Such procedures have been discussed in detail below.
Submandibular sialoliths Submandibular gland lithiasis is the most common disorder of submandibular gland and most frequent location being extra glandular. Despite the fact that these calculi are large they are rarely painful since lumen of Wharton’s duct is larger and more expandable than the Stenson’s duct. Usual symptoms are pain and sudden gland enlargement during eating. Usually there is return of function in most patients after removal of sialolithiasis. Salivary glands –Diseases and Management
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Those located in the anterior part of the duct Usually stones located anterior to the second mandibular molar are best removed under local anaesthesia. Those lying anterior to a line joining mesial surfaces of second molars are designated as anterior calculi. Preoperative assessment of anterior calculi depends on history, clinical examination and plain radiographs. Usually a preoperative sialogram is not indicated because of the possibility of the stone being propelled into a more posterior part of the duct by the force of the injection.
Procedure A suture is passed around the duct posterior to the stone to prevent its posterior dislodgement during manipulation after passing one suture into the floor of the mouth to test the tissues up for easy passage of the circumductal suture. Duct can be easily located by bisecting the angle formed by the sublingual plica and the line attachment of the tongue. The circumductal suture is then secured to a haemostat and placed over the adjacent teeth resulting in kinking of the duct. A second suture is then placed between the submandibular duct papilla and frenum. Gentle traction applied to these sutures will make tissues at surgical site taut thereby allowing mucosa to be cut easily. Incision is made along the line of the duct over the stone. Scalpel should not be plunged deeply but should only divide the mucous membrane and enter just into the underlying tissues. The duct is then uncovered by both blunt and sharp dissection with a fine pointed scissors through the loose connective tissue always being aware of sublingual veins lingually. It is then mobilised. Frequently at this stage the calculus is visible through the duct wall and by a longitudinal incision, it is released. If it is adherent to the duct wall, then it is slowly released with a small curette without further damaging the duct.
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A few interrupted sutures at the floor of the mouth then close wound. Ductal incision is not sutured to prevent formation of a stricture.
Those located in the posterior part of the ductThese are best removed under general anaesthesia, as few patients will tolerate retraction required under local anaesthesia. An obstruction sufficient to cause symptoms can occur in any one of the two ways: - stone may increase to such a size that only a minimal amount of saliva can be secreted or an infection may set in. If the stone is not visible on a central occlusal film, then it is not feasible to remove it by the method used for anteriorly placed stones and it must be treated as a posteriorly placed stone or an intraglandular stone. Majority of the posterior stones can be viewed in a posterior oblique occlusal film. This is supplemented with an oblique lateral jaw film so that its position relative to the mandible can also be assessed. However the best means of locating its position and status of the gland is by sialography. If it depicts a “ sausage string appearance� in the sialogram a good chance of recovery exists. When the intraglandular ducts are irregular, grossly dilated and cavitated then removal of the gland is the best choice.
Procedure Best done under general anaesthesia. Tongue is retracted sideways. A lacrimal probe is inserted via the ductal orifice and elevated to assist in locating the duct and then mucosa is excised in the premolar region. Duct is identified and drawn forwards using a suture passed around it. Duct is then followed posteriorly and lingual nerve identified where it crosses beneath the duct. Once lingual nerve is identified then initial incision is enlarged, lingual nerve is mobilised laterally and retraction sutures passed to expose the surgical site. An assistant then pushes the lower pole of the gland upwards so that the upper pole is brought into view. A suture is then passed over posterior margin of Salivary glands –Diseases and Management
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mylohyoid to retract it forward. If the stone is visible, it is delivered via a longitudinal incision. If not duct is opened at most likely location and explored until recovered. Wound is then irrigated; retraction sutures removed and incised duct left open, mucosal tissues are then closed with interrupted sutures.
Those located in intraglandular position of the submandibular ductHere the entire gland is removed. If the stone is a chance finding and is small, asymptomatic and sialographically normal, it can be left in place and observed for any changes in its location or function of the gland. Any change for the worse indicates the need for gland excision.
Procedure A two-inch long convex incision is made parallel to skin crease, approximately 1.5-2cm below the inferior border of mandible. Incision deepened down through superficial cervical fascia, reflected inferiorly, anterior facial vein identified and divided between ligatures. An upper flap of connective tissue is then raised close to the gland surface thus protecting any branches of facial nerve raised along with the flap. The facial artery is found by dissecting and then retracting the lower pole of the gland upwards and forwards. The posterior belly of digastric is identified and it along with the stylohyoid is retracted down and back. The facial artery is seen passing behind the muscle towards the gland. It is clamped and divided, then ligated. Then the anterior aspect of the lower pole of the gland is reflected upwards and backwards. Through finger dissection and keeping close to the gland, a covering of loose connective tissue is maintained over the hypoglossal nerve that lies medial to the gland. The gland is then pulled downwards, exposing the V-shaped fold of connective tissue containing the lingual nerve and submandibular duct. These two Salivary glands –Diseases and Management
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structures are then dissected out with care. At this stage one should be able to clearly delineate three basic structures medial to the gland namely lingual nerve superiorly, duct centrally and hypoglossal nerve inferiorly. Now only the duct and deep part of the gland still remain attached. The posterior border of the mylohyoid is retracted and a branch of the sublingual artery ligated. Then the submandibular duct is clamped, divided and double ligated so that only a short stump remains. Tissues are then closed in layer, a drain inserted if necessary and a pressure dressing applied.
Parotid sialoliths •
Stensen’s duct is the location of 6-10% of salivary calculi. Of these 40% are opaque. They are seen at 4 basic locations: -
•
Impacted in the papilla
•
In the sub mucous part of the duct
•
Intraglandularly
•
In the extra glandular part of duct external to the buccinator.
Those in the papilla and submucous part of the duct Calculi in this location can be released by slitting the papilla. One blade of a pair of fine sharp pointed scissors is inserted a portion of the way into the duct and a small cut is made backward from the orifice. Usually the calculus pops out as soon as the blade of scissors is removed, if not then gentle pressure on the gland will force out the calculus along with a quantity of saliva. The wound heals rapidly.
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Those located extraglandularly external to the buccinator – Calculi located in this region can be approached via an incision in the intraoral aspect of the cheek. Injection of a local anaesthetic with a vasoconstrictor will reduce bleeding and also raise the mucous membrane off the surface of buccinator to aid in soft tissue dissection. A traction suture is placed anterior to the papilla, a U-incision is made through the mucosa, and the triangle containing the papilla and the duct is then raised off the buccinator. Upper and lower flaps are mobilised and stay sutures placed to hold them out of the way. Dissection is proceeded until the point where the duct pierces the buccinator is reached. The superior and inferior margins of buccinator dehiscence are identified and traction sutures placed at each margins and retracted to enlarge the dehiscence. Then duct is traced laterally and retracted medially into the mouth with a suture. With this approach calculi in a large portion of Stenson’s duct can be removed easily even well outside the masseter musculature. Once calculi are located, adhesions to tissues around are divided; longitudinal incision made over the duct and stone removed. The duct is not sutured but tissues around are closed with absorbable sutures.
Those located in the intraglandular portion of the ductStones located intraglandularly cannot be reached by an intraoral approach. A parotidectomy type incision is recommended. Skin and subcutaneous tissues are raised from deep fascia covering the gland until its anterior border is uncovered. Then deep fascia is incised horizontally over the supposed portion of the duct. Duct at this point lies on a line joining the angle of mouth and ala of nose. The buccal branch of facial nerve usually lies on its surface and transverse facial vessels usually lie about 1cm higher than the duct. Once duct is identified, it is then traced back into the gland. Branches of facial nerve tend to cross immediately superficial to the duct and must be preserved. When the section containing the calculi is reached it is incise longitudinally in the usual way and delivered after passing necessary sutures in front and behind the stone around the duct to prevent slippage. Capsule of the gland is closed with continuous fine plain catgut and skin incision is closed in layers with a vacuum drainage. Salivary glands –Diseases and Management
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Tumours of salivary glands Salivary gland neoplasms are uncommon and account for less than 3% of all tumours of head and neck region. Of these tumours about 75-85% occur on parotid, 10-20% in minor salivary glands, most commonly in palate (58%), tongue (10%) and upper lip (9%). Sublingual gland has the highest ratio of malignant to benign neoplasms. In fact 80% of parotid, 65% of submandibular, 50% of minor salivary and 20% of sublingual gland tumours are benign. The only curative treatment of salivary gland tumours is surgical extirpation. Resection of parotid gland tumours is complicated by the presence of facial nerve within the gland. With the exception of Warthin’s tumours, enucleation of parotid tumours is not advised. Mixed tumours are often poorly encapsulated and malignant tumours often invade surrounding glandular tissue, hence adequate margins of normal salivary tissue must be resected to reduce the chances of local recurrence. Total resection of submandibular gland is the preferred treatment for all submandibular neoplasms. Minor salivary gland neoplasms of palate or mucosa frequently involve periosteum or bone and hence portions of these must be included along with the surgical excision.
Parotidectomy with the preservation of facial nerve This operation is also called superficial or conservative parotidectomy. Superficial parotidectomy is used to describe the removal of the gland superficial to facial nerve. But both superficial and deep parts can be removed as necessary with preservation of facial nerve. After adequate preparation of surgical site, a solution of 1 in 200,000 parts adrenaline in saline is injected under the skin over the parotid anterior to external ear and close against external auditory meatus. Not more than 10ml is injected.
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Incision starts within the hairline above and anterior to the auricle and is taken down and back to free margins of tragus, follows it and under its cover is carried in a gentle curve over the mastoid to join a convenient skin crease passing down and forwards into the neck behind the mandible. Incision in the neck crease is deepened first, dividing the platysma until the deep fascia is reached. The great auricular nerve is then identified as it crosses the posterior border of sternomastoid to lie in the wound about 1cm below and 1cm in front of the lobe of the ear, immediately below the deep fascia, branching over the gland surface. The nerve with the branches is tucked under the lower edge of the wound to keep it moist. Once deep fascia is identified the rest of the wound is deepened to this level and skin reflected forwards from it. Often one or more facial branches will be identifiable through translucent deep fascia as they emerge from anterior border of the gland. They are uncovered by opening the fascia, each branch is identified, labelled by under running it with black silk and ends of it are clamped in mosquito artery forceps. The main trunk of the facial nerve lie further deeper down in the angle between bony external auditory canal and anterior surface of mastoid process. It is found by separating lower pole of gland from anterior border of sternomastoid and from mastoid process and cartilaginous part of external auditory meatus. Parotid is retracted forwards as dissection proceeds and the nerve is identified as it emerges in the angle between tympanic bone and anterior border of the mastoid process and just superior to the upper border of the posterior belly of the digastric. The stylomastoid branch of posterior auricular artery passes superficial to the nerve to enter the stylomastoid foramen and rough instrumentation can tear this small vessel causing haemorrhage. Since the facial nerve and its branches are invested by loose connective tissue and lie in tunnels within the parotid, they are freed by introducing the tip of Salivary glands –Diseases and Management
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the blades of a curved mosquito artery forceps and opening it after which a short length of the gland substance mat be cut through with scissors to expose the gland. The nerve trunk travels laterally within the parotid, passing around posterior border of mandible and just below the neck of the condyle before it splits into an upper temporofacial and cervicofascial division. Generally it is better to follow the lower division first and trace the cervical or at least marginal mandibular branch anteriorly to a point in front of the parotid, hence the lower pole is mobilised after which progressing upwards branch by branch, further mobilisation is achieved. Those branches that pass into the tumour must be divided and the point at which they emerge identified and divided and both ends are tagged for subsequent repair. Interconnecting branches joining two peripheral branches vertically should be conserved if possible. In general nerve passes superficial to retromandibular vein; careful mobilisation of both nerve and vein with division and ligation of the latter is needed. Tiny veins are sealed by diathermy. For pleomorphic adenomas a margin of about half a cm of apparently normal tissue should be removed around palpable mass as the tumour is lobulated and some of these lobules may be left behind if dissection passes too closely. Low-grade mucoepidermoid tumours or acinic cell tumours should be removed with a somewhat greater and more uniform margin. Once tumour is removed, the wound is flushed liberally with saline and haemostasis checked. Branches of facial nerve may be repaired with grafts if necessary from great auricular nerve. A vacuum drain is then passed out through the skin below the ear; wound is closed in layers and light pressure dressing applied.
Total parotidectomy This is indicated when: •
A slow growing mass not clinically malignant is present in deeper parts
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•
When a small neoplasm is recognised clinically as malignant and to secure necessary margin, removal of whole gland is planned.
•
Large tumour in deep part of parotid gland presenting as a swelling of the soft palate (often dumb-bell in shape with isthmus lying in the gap between styloid process and back of mandible).
Procedure A skin flap is raised in usual way, but incision in the neck skin crease is continued as far forward as the first molar region. Facial nerve is dissected out; periosteum is then divided at lower border of angle of mandible and masseter elevated from bone. A vertical cut similar to that used for vertical sub sigmoid osteotomy is made just behind the mandibular foramen, medial pterygoid is then freed from posterior fragment, which is then displaced forwards, lateral to anterior fragment. This opens up the interval between the styloid process and mandible. Lower pole is then mobilised and digastric and sytlohyoid followed back to their origins, divided and turned forwards. External carotid emerging above the muscles is identified and divided and ligated. At this stage mouth is uncovered and entered. A solution of adrenaline 1:200,000 in saline is injected into soft palate over swelling and a vertical incision, circumscribing any previous biopsy scar is made. Edges are undermined leaving a thin layer of muscle and connective tissue over the tumour. Mass is freed working through both wounds. Great care is exercised above and particularly behind the lesion for fear of damaging the internal jugular vein or internal carotid artery, both of which lie deep to styloid process. Following removal, wound is irrigated; oral tissues are closed with chromic catgut. The mandibular fragments are then wired together. Preauricular wound is closed in layers and drainage established.
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Parotidomandibulectomy This is indicated when there is invasion of mandible by a malignant neoplasm.
Procedure: After preparation of surgical site, a skin flap is raised as for excision of a benign neoplasm of the deep part of parotid. Gland is then mobilised posteriorly and inferiorly and main trunk of facial nerve identified. As many branches are dissected out as possible, sometimes sacrifice of the whole nerve may be necessary. Next the TMJ capsule is opened, and condyle mobilised. Masseter is separated from the zygomatic arch and mandible is divided in the third molar region. Parotid and mandibular ramus are tilted up and forward and separated from the styloid process and its attachment muscles. Then further elevation of the ramus is possible after which the origin of the medial pterygoid muscle from the tuberosity is palpated and separated. Before this is done the external carotid is identified where it emerges from behind the stylohyoid and enters the deep part of the gland. It is first ligated and transected to prevent troublesome haemorrhage from maxillary artery as the medial pterygoid is sectioned. Strong downward traction will now permit separation of the insertion of temporalis into the coronoid and lateral pterygoid to the condyle. As hemostasis is completed the maxillary artery is sought and ligated. Facial nerve is repaired using great auricular nerve as graft. A bone graft can then be placed unless a postoperative course of radiotherapy is to be employed. Where a bone graft does not replace ramus, patient will be left with a deep depression in front of the ear, but this can be covered by a suitable hairstyle. There will be a tendency for the mandible to swing towards the affected side and hence early training is needed to overcome this problem.
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If condyle is invaded, then articular fossa and eminentia can also be removed. Styloid process and muscles can also be excised to increase the margins, but should be done after resection of the main mass.
Temporoparotidectomy Small-scale resection of external auditory canal may be included with excision of pinna and overlying skin of parotid when these structures are involved. The mastoid process can also be detached without much difficulty, thus exploring facial trunk to make suturing and nerve grafting easy. Extension of a parotid neoplasm back into bone is therefore amenable to excision of parotid gland, mandibular ramus and TMJ together with temporal bone. However the operation carries high risk for the need to section dense bone and separate it from internal carotid artery, internal jugular vein and sigmoid, superior and inferior petrosal sinuses. Adequate cover needs to be provided for the dura as the wound is closed. The hypoglossal nerve is mobilised and anatomised to the peripheral branches of facial nerve at the end of the operation.
Parotidectomy in continuing with neck dissection A radial neck dissection should be performed where cervical lymph nodes are involved or where there is a mass at lower pole of parotid due to an aggressive tumour of much size that invasion of upper cervical nodes cannot be excluded. Consideration should be given to pre-operative radiation of the neck to a dose of 400-500 rads.
Extracapsular excision of submandibular salivary gland There is a great incidence of recurrence for the submandibular gland than for the parotid after excision of slow growing neoplasm like pleomorphic adenomas. The gland is removed together with its investing fascia, which is separated from the anterior and posterior bellies of digastric and stylohyoid muscle. The
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hypoglossal nerve is identified and preserved. The facial artery is identified where it emerges from under the cover of the stylohyoid and again on the lateral surface of the mandible. Marginal mandibular nerve is isolated and preserved and then fascia divided at the lower border of the mandible. Gland is freed off the mylohyoid muscle anteriorly and the angular tract of fascia posteriorly. If the lingual nerve is involved in the tumour mass then it is sectioned in front of and behind the gland and cut ends sutured. If a greater margin of tissue than the immediate capsule is needed laterally then the periosteum of the mandible is divided at the lower border and stripped up from the submandibular fossa. The duct is divided close behind the papilla and the wound closed in layers with drainage in usual way.
Radical excision of neoplasms of submandibular/sublingual gland Excision of frankly malignant invasive neoplasms of submandibular or sublingual salivary gland will include the tongue on that side, floor of the mouth and mandible together with a radical neck dissection of palpable nodes if present.
Excision of palatal pleomorphic adenomas Small palatal pleomorphic adenomas cause only pressure resorption of palate and rarely invade bone. The incision is deepened to bone and specimen reflected off the hard palate with the periosteum. The neoplasm frequently sits over the greater palatine foramen and the periosteum is freed here until the lesion can be drawn down and neurovascular bundle is clamped, sectioned and coagulated with diathermy before it is sectioned. Interrupted silk sutures are then placed and tied together to retain a pack soaked in Whitehead’s varnish. When full thickness of the soft palate has to be removed for adequate tumour clearance then the defect is repaired by an “island flap” described by Worthington (1974).
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Excision of palatal mucoepidermoid carcinoma Low-grade mucoepidermoid carcinomas may be treated by excision of a full thickness disc of palate, including palatal and alveolar bone. Nasal and oral mucous membranes are then sewn together around the defect and stabilised with a gutta-percha obturator. Surgical repair of such defects should be undertaken only at least after 5 years due to the possibility of a recurrence.
Excision of palatal adenoid cystic carcinoma Danger with these neoplasms is that the surgical margin may be inadequate and spread can occur along perineural tissues of palatine nerves into skull base. Hence a combination of surgery and radiotherapy is the best. Surgical excision should include a hemimaxillectomy including orbital floor, which is the minimum. Where soft palate and pterygoid region is involved, “Crockelt’s extended maxillectomy approach” is essential to remove adequate excision under direct vision.
Neoplasms of cheek and lips Slow growing lumps can be removed with a margin of normal adjacent tissue, using scissors to effect dissection. A biopsy is mandatory if there is any doubt in the mind of the operator. Clinically aggressive neoplasms can be biopsied since adequate treatment may involve radiotherapy and full thickness excision and repair.
Strictures Strictures can result from resolutions of the ulcerations of the duct lining that occurred secondary to the presence of sialoliths. Sometimes the ulcerations will result in the discharge of stone into the mouth forming a fistula. But if fistula closes a stricture will result. If transverse incisions are put on the duct, strictures can develop. Those close to the papilla can be treated by papillotomy. Those posterior in the duct can be treated by implanting the divided end of the duct into the floor of the mouth i.e., sialodochoplasty, but those close to the submandibular gland will require gland excision. Salivary glands –Diseases and Management
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Dilation Strictures of parotid duct can be managed by dilation with probes. This is done slowly and the procedure may have to be repeated two or three times at 2 weeks intervals, but dilation may be effective for a long period of time.
Papillotomy A fine probe is passed into the duct to mark the lumen. With a probe or a thread serving as a guide a fine pointed scissors is passed into the duct and papilla is laid open. Cut is continued posteriorly until the dilated portion of duct proximal to the strictures is reached. Using a 5.0 chromic suture, cut edge of the duct lining is sewn to the mucosa of the mouth. Resultant opening remains somewhat wide for a month or so, then narrows to a acceptable degree.
Sialodochoplasty Here the duct is completely divided and implanted into the floor of the mouth. Two sutures are made one beneath the papilla and other behind surgical area putting tension on the mucous membrane. A incision is made over the duct and region of stricture is identified. A suture is placed around the duct and then a longitudinal incision is made in the duct behind the stricture. Posterior end of the slit is sewn to the posterior part of the wound edge with a 5.0 chromic suture. Further sutures are placed so that either side of slit may be sewn to either side of the incision in floor of the mouth. Then a suture is passed down through the under side of the duct just beneath the anterior end of slit, duct is then transacted to the anterior longitudinal portion of the incision and remainder of cut end of duct is then sewn into place more inferiorly. Nonfunctional end of duct is ligated and remainder of incision in floor of mouth in front of and behind the implantation is closed.
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Complications Of Salivary Gland Surgery Frey’s syndrome About one in ten patients who have parotid gland surgery suffer from gustatory sweating. This is caused by damage to auriculotemporal nerve or to communicating branches of facial nerve. Subsequently during repair, fibres from otic ganglion come to supply sweat glands. Only rarely is this complication severe to require treatment. Only effective treatment is to divide parasympathetic fibres from glossopharyngeal nerve either during their intracranial course in lesser superficial petrosal nerve or in the tympanic and hypotympanic branches of glossopharyngeal nerve, where they lie behind the round window in the inner aspect of middle ear.
Facial paralysis Symmetry of the face at rest can be restored by use of facial sling. Strips are cut from a ribbon of fascia from patient’s own thigh. These are inserted as loops by a technique similar to that used to insert circumferential wires and are tied onto the parotid fascia and temporal fascia. Both the upper and lower lips are pulled over to bring the centre point back into the midline. Nasolabial fold is re-established and lower lid drawn up into contact with the globe. A pleasant appearance is thus achieved while the face is at rest and general effect is not so unpleasant for the observer.
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Conclusion Although a wide variety of disorders can affect the salivary glands, most of these are relatively uncommon in the spectrum of medical pathology. A thorough knowledge of the normal and abnormal physiology of the salivary glands, and the surgical anatomy of the structures, is necessary for the successful management of these conditions.
REFERENCES
1. A Textbook of Oral Pathology: Shafer, Hine and Levy: 4 th edition 1993. 2. Burket’s Oral Medicine: Edited by Lynch: 9th edition 1994. 3. Differential Diagnosis of Oral Lesions: Wood and Goaz: 3 rd edition 1985. 4. Management of Salivary Gland Lesions: Granick and Hanna: 1993. 5. Kruger’s Textbook of Oral and Maxillofacial Surgery: Gustav O. Kruger :1990. 6. Basic Pathology: Kumar, Cotran and Robbins: 5th edition: 1992. 7. The diagnosis and surgical management of salivary gland disorders. S. E. Feinberg. In Basic Principles of Oral and Maxillofacial Surgery. Peterson, Marciani, Indresano (eds). 1994. 8. Surgery of Mouth and Jaws. J. R. Moore (ed). 1985.
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