Differential Diagnosis: Mucosal Mass of Lower Lip

ODA FEATURE

Differential Diagnosis: Mucosal Mass of Lower Lip By: Glen D. Houston, DDS, MSD | Diplomate, American Board of Oral and Maxillofacial Pathology | gdhdds@heartlandpath.com

CASE HISTORY

A 7-year-old patient, referred by his pediatrician, presented for evaluation. During the examination, a fluctuant soft tissue mass was observed involving the labial mucosa of the lower lip. The parent noted that the area in question had been present for several days and developed following an athletic injury associated with the face.

QUESTION #1

A working differential diagnosis for this lesion might include: a. Squamous cell carcinoma b. Mucous extravasation phenomenon (mucocele) c. Adenoid cystic carcinoma d. Traumatic neuroma e. Epidermoid cyst

f. Hemangioma (cavernous)

ANSWER #1

Your differential diagnosis should include: b. Mucous extravasation phenomenon (mucocele) d. Traumatic neuroma e. Epidermoid cyst

f. Hemangioma (cavernous)

All of the above lesions can present as a fluctuant mass involving the lower lip.

The mucous extravasation phenomenon (mucocele) (b) most frequently occurs on the lower lip but may also involve the palate, buccal mucosa, tongue and the floor of the mouth. This lesion is most commonly observed in children or young adults and presents as a dome-shaped mucosal swelling.

The traumatic neuroma (d) typically presents as a smooth-surfaced, nonulcerated, submucosal nodule. It can develop in any anatomic location but is most commonly observed in the mental foramen area, tongue and lower lip. It can be seen in any age group, but is usually found in middle-aged adults. journal | Nov/Dec 2020 The epidermoid cyst (e) is usually associated with the skin of the head, neck and back. This lesion presents as a nodular, soft, fluctuant, yellow or white mass. Males tend to be affected more frequently than females.

The hemangioma (f) is primarily a tumor of childhood. The most common location for this lesion is the head and neck, accounting for almost one third of all cases. A predilection for females is also observed for this soft, fluctuant vascular lesion.

Squamous cell carcinoma (a) would not be included in the differential diagnosis because this condition typically presents in adult males who have experienced chronic actinic exposure. The clinical presentation is a crusted, asymptomatic, indurated ulceration characterized by a slow growth rate.

Adenoid cystic carcinoma (c) is also not a consideration here. Although adenoid cystic carcinoma can occur in any salivary gland, the majority arise within the minor salivary glands with the palate being the most common location. The lesion typically presents as a slow-growing mass that is painful. It is rarely observed in people younger than age 20.

QUESTION #2

Your treatment plan should include: a. Referral back to the pediatrician for examination of all skin surfaces b. Exfoliative cytology c. 4 mm punch biopsy in the center of the mass d. No surgical intervention; follow closely for 3-6 months

e. Biopsy the lesion

ANSWER #2

Your treatment plan should include (e) biopsy the lesion. A solitary mass on the lower lip of a young patient is best managed by an excisional biopsy.

Referral back to the pediatrician for examination of all skin surfaces (a) will be of little benefit in this case since it is not known what the mass of the lower lip represents from a histologic standpoint. Exfoliative cytology (b) is of very limited value in the diagnosis of a mass involving the lower lip; it is primarily utilized in the diagnosis of certain viral conditions, vesiculobullous diseases, and a limited number of infectious diseases. It is an adjunct but not a substitute for a surgical biopsy procedure. A punch biopsy in the

center of the mass (c) and no surgical intervention; follow closely for 3-6 months (d) are of no benefit in this case. There is nothing to be gained in the management of a fluctuant mass of the lower lip by utilizing either of these techniques.

QUESTION #3

A tissue sample is submitted to the oral histopathology center for microscopic examination. The pathology report describes a circumscribed, cystic cavity composed of a thin wall of granulation tissue surrounded by numerous lobules of accessory salivary gland tissue. The lumen of this cavity is filled with an eosinophilic, amorphous coagulum containing variable numbers of neutrophils, lymphocytes and histiocytes. Considering the clinical presentation and microscopic description, the most likely diagnosis for this lesion would be: a. Foreign body with associated foreign body reaction b. Varix with organized thrombus c. Epidermoid cyst d. Mucous extravasation phenomenon (mucocele)

e. Mucoepidermoid carcinoma

ANSWER #3

The lesion is correctly diagnosed as (d) mucous extravasation phenomenon (mucocele). See the “Discussion” section.

The other possibilities are not considered here because (a) foreign body with associated foreign body reaction is composed of foci of exogenous, foreign material with a typical multinucleated (foreign body) giant cell reaction (granulomatous inflammation). Varix with organized thrombus (b) is an abnormally dilated, tortuous vein with secondary thrombosis within the lumen. The epidermoid cyst (c) is composed of a cavity lined with stratified squamous epithelium and exhibits a lumen that is filled with desquamated keratin. Mucoepidermoid carcinoma (e) is a malignant salivary gland neoplasm composed of a mixture of mucusproducing cells and epidermoid or squamous cells. These features are not observed in the current case.

DISCUSSION

The mucous extravasation phenomenon (mucocele), generally believed to be traumatic in origin, is a lesion involving the salivary glands and their ducts. Traumatic severance of the salivary gland duct, such as that observed by biting the lip or buccal mucosa or, in this case, an athletic injury, precedes the development of the mucocele. Once the salivary gland duct is severed, a continuous pooling of mucus occurs in the surrounding fibrous tissue, producing a well demarcated cavity filled with mucus.

The mucocele arises most frequently on the labial mucosa of the lower lip. It may also involve the floor of the mouth (where it is known as a ranula), buccal mucosa, palate, or the ventral surface of the tongue. Although the mucocele may occur in any age group from newborn to adult, it appears to be commonly observed in the first three decades of life. An equal distribution in occurrence between males and females has also been reported. The mucocele may present a variable picture in terms of its clinical appearance. The lesion in a superficial location will manifest as a circumscribed, fluctuant nodule with a bluish, translucent cast. A deeper location may also present as a fluctuant mass, but the surface appearance and color are those of normal mucosa.

As previously mentioned, this phenomenon typically occurs following a traumatic episode of the involved area. The mucocele will usually grow to a certain size and may persist for long periods of time unless treated. If the contents of the mucocele are expressed, they are usually found to consist of a thick, mucinous material.

Microscopically, the mucocele is composed of a circumscribed, cystic cavity in the fibrous connective tissue of the submucosa. The lumen of the cystic cavity is surrounded by a thin wall of granulation tissue and is filled with an eosinophilic coagulum (mucus) containing acute and chronic inflammatory cells. A “feeder duct” from the associated salivary gland tissue is usually observed.

Local excision with extirpation of the underlying lobules of minor salivary gland tissue is the treatment of choice. Failure to remove the glandular tissue may contribute to recurrence and/or persistence of the lesion. It is of interest that the mucocele is restricted almost exclusively to the labial mucosa of the lower lip and is seldom, if ever, observed involving the upper lip. Conversely, salivary gland neoplasms are for the most part confined to the upper lip and only rarely occur on the lower lip.

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