SKIN PATHOLOGY NEOPLASIA

Skin Neoplasia Dr. W. Merchant St. James's Hospital Leeds

Case1 • 51F Lump on eyelid

Main Histological features • Lobulated tumour connected to epidermis • Composed of small cells with central round nuclei often with pale eosinophilic to clear cytoplasm.

• Uniform cells without nuclear atypia.

• Mitoses are rare.

• No necrosis • Peripheral palisading with thick hyaline basement membrane • Central zone has dense sclerosis with cords of tumour cells ‘infiltrative’ pattern.

Case 1 • • • • • • •

Histopathological differential diagnosis SCC, Clear cell BCC with Tricholemmal differentiation Tricholemmal carcinoma Tricholemmoma Sebaceous tumour Poroma

Tricholemmal Tumours • Tricholemmoma’s are associated with Cowden’s syndrome. Desmoplastic variant is probably not. Can arise in Organoid naevus as in this example.

• Approximately 50% have been found to harbour wart virus.

• Trichilemmona’s show follicular differentiation.

Remembering normal structure, most resembles outer root sheath of stem. They are CD34 positive and BerEp4 negative [allowing distinction from BCC].

This is seen in normal outer root sheath.

Desmoplastic trichilemmoma • Easily confused with malignant tumour due to pseudo infiltrative growth but; • No nuclear atypia, • No perineural or vascular invasion.

• Profile still reasonably circumscribed. Infiltrative area in centre where sclerosed.

• No Necrosis

Desmoplastic Trichilemmoma Vs Trichilemmal Carcinoma • Trichilemmal carcinoma [TC] is described as a low grade neoplasm arising in sun damaged skin which very rarely recurs and metastases not documented.

• Difficult to separate from conventional SCC, BCC and desmoplastic trichilemmoma.

• Not included in WHO classification.

CD34

Adnexal Tumours Benign VS malignant • Infiltrative growth pattern • Perineural invasion • • • •

Lymphovascular invasion Mitotic activity, especially atypical forms.

Nuclear atypia Necrosis

• BUT EXCEPTIONS OCCUR !

Case 2 • 40M, several skin lumps

Microscopy • Lobulated, circumscribed tumour.

• Cells variable; basaloid to clear cells with vaculated cytoplasm.

• Crenulated nucleus due to vacuoles • Ducts; with sharp keratinised irregular border.

• Holocrine secretion • Foreign body reaction

Sebacous adenoma • Spectrum; sebacous adenoma [>50% mature], sebaceoma [< 50% mature], Sebaceous carcinoma.

• Association with Muir-Torre syndrome.

Sebaceous Tumours; Worrying features for malignancy; • • • • •

Cytological atypia Infiltrative growth pattern Necrosis Atypical mitoses Site; eyelid

Immunohistochemistry • EMA usually highlights vacuoles.

• CK 7, Androgen receptor often positive [unlike SCC].

• BerEP 4 usually negative, [unlike BCC].

Immunohistochemistry EMA

A.R.

BerEp4

CK7

SEBACEOUS CA

+ 90%

80%

5%

60%

BCC

0%

50%

100%

10%

SCC

90%

10%

0%

1%

Muir-Torre Syndrome • Association between Sebaceous tumours and keartoacanthoma’s with visceral cancer, especially bowel cancer.

• Bowel cancer, part of Hereditary nonpolyposis coli inherited syndrome.

• Also cancer of genito-urinary system and occasionally elsewhere.

Muir-Torre Syndrome • If sebaceous tumour, increased risk of having Muir-Torre if; • <50yrs old • Non ocular.

• Multiple sebaceous/KA’s • ? Very cystic sebaceous tumours • Hybrid KA/Sebaceous tumour • Still have to raise as possible in all sebaceous adenoma’s

Case 3 • 45F Cyst on calf

Microscopy • Lobulated, circumscribed deep dermal tumour.

• Clear cells, small regular nuclei.

• Partly cystic. Cyst lined by cells with eosinophilic cuticle.

Clear cell tumours • • • • • • •

Eccrine ductal; Hidradenoma, poroma Sebacous Tumours Follicular; Trichilemmoma BCC; clear cell SCC, clear cell Clear cell/balloon cell naevus/melanoma Metastasis, RCC

Hidradenoma • Benign • None infiltrative growth pattern • No cytological atypia.

Hidradenoma • Clear cell variant associated with t[11;19] • TORC1-MAML2 gene fusion • Seen also in muco-epidermoid carcinoma and Warthin’s tumour.

Case 4 • 25F Cyst on cheek

Microscopy • • • • •

Circumscribed, but unencapsulated.

Cords lobules small epithelial cells.

Regular cuboidal cells, no nuclear atypia Ductal structures identified.

Chondroid matrix

Chondroid syringoma • Many might be of apocrine origin • Can show focal differentiation towards follicle; – Hair bulbs, ghost cells,sebaceous.

• Stroma, can be hyalinised or contain fat.

Case 5 • 44M, Lump on forearm

Microscopy • Unencapsulated nodular tumour • Spindle cell proliferation. Arranged in interlacing fascicles.

• RBC’s between spindle cells • Minimal nuclear atypia.

• Inflammation around margin, many plasma cells.

• No necrosis

Differential Diagnosis • Kaposi’s sarcoma • Spindle cell haemangioma; more cavernous with only focal spindle cell component..

Vacuolated endothelial cells. No plasma cells.

• Kaposiform Haemangioendothelioma. Very similar. Seen in young children. Very rare in skin.

Kaposi’s Sarcoma • Antibody for HHV8 very useful. Not seen in any other vascular tumours.

Case 6 • 70 F, Indurated lesion on upper lip. Punch biopsy.

Case 6. Main histological features • Cords of cells extending through entire thickness of dermis.

• Occassional small keratocyst.

• Ductal structures with cuticle lining.

• Cytology, small cells, no nuclear atypia.

• No mitotic activity.

Differential diagnosis • Microcystic Adnexal Carcinoma [MAC] • Morpheic BCC [MBCC] • Desmoplastic trichoepithelioma [DTE]

D.T.E. Vs MAC VS BCC DTE

MAC

MBCC

Symmetry Perineural invasion

Yes No

No Yes

No Yes

Deep invasion ie s/c

No

Yes

Yes

Clefts

Stromadermis

No

Nestsstroma

Nuclear atypia mitoses,necrosis

No

Rare

Yes

Advanced follicular

Yes

Variable

No

Ducts Merkel or Naevus cells

No Yes

Yes No

No No

MAC • Adults, wide age range.

• Upper lip commonest site, but also periorbital and axilla.

• Can cause pain or burning sensation due to perineural spread.

• Can occur post DXT. • Frequently recurs locally but doesn’t metastasize.

MAC, Important features • Cytologically bland • Infiltrative growth pattern • Ductal differentiation, Immuno can help, luminal EMA or polyclonal CEA. • S100 for perineural invasion.

• BerEp4 negative in basaloid peripheral cells, unlike DTE and MBCC. Can be positive in luminal cells.

Desmoplastic Trichoepithelioma • Small symmetrical tumour often with central dell.

Unfortunately cannot assess these on punch biopsy.

• Tumour usually located in superficial half of dermis but may extend into deep dermis but not fat.

• Tumour composed of cords of small basaloid cells • Surrounding thick collagen which is closely applied to cords.

• No nuclear atypia. No mitoses. No perineural spread. No necrosis. No ducts • Signs of advanced follicular differentiation; Hair bulb, trichohyaline granules, ghost cells, sebaceous cells.

• Second population of small dermal melanocytes . This is seen in 10% of DTE’s.

• Immunohistochemistry for Cytokeratin 20 will identify Merkel cells – Costache M, Bresch M Boer A Histopathology,52 [7] 865-876 2008

Case 7 • 25 male with lump on arm.

Case 7. Main histological features • Dermal tumour. No capsule. Fades into adjacent dermis.

• Composed of admixture of cells; spindle cells with small amount of indistinct cytoplasm.

Foamy cells, some containing iron. Prominent vessels. Scattered lymphocytes.

• Spindle cells wrap around collagen at edge.

Collagen looks slightly darker.

• Epidermis over top shows some reactive changes.

Cellular/aneurysmal dermatofibroma • Occur predominantly in young adults on limbs.

• Can recur locally

Differential diagnosis • DFSP • LMS

Important points • • • • •

Variable cellularity and variable cell type.

Collagen changes at tumour margin.

Overlying epidermal changes.

Can have necrosis.

Can have nuclear atypia [pseudosarcomatous dermatofibroma].

Case 8 • 50F , ?BCC on arm

Case 8 • Consists of basaloid buds arising from the epidermis.

• Composed of small germative cells, nuclear palisading. Has fibroblastic stroma with similar characteristics as a trichoblastoma.

• Underlying tumour composed of spindle cells with prominent collagen.

Differential diagnosis • BCC • Follicular induction over dermatofibroma

Dermatofibroma with follicular induction • • • •

Fairly common Can cause problems if only superficial biopsy Can rarely be seen over other tumour types.

Very similar appearance can be seen in organoid naevi.

Follicular induction vs BCC Follicular induction Present

BCC

Fibroblastic

Fibromyxoid

Necrosis

Absent

Present

Extends beyond dermal tumour

No

Yes

p53

Focal

Diffuse

Papillary mesenchymal bodies Stroma

Absent

Case 9 • 18F Plaque on abdomen

Main Features • Tumour involving dermis and s/c • Infiltrates s/c fat with lacy, interlinking pattern • Cells, small, uniform. Arranged in short fascicles and storiform pattern.

• Small amount of cytoplasm [tumour blue on low power].

• Nuclei, small, oval and regular.

• Epidermis, normal

DFSP • Young adults, wide variety of slides, but very rare on hands and feet.

• No nuclear atypia • Pattern of infiltration of fat characteristic.

DFSP

VS

DF

S/c Infiltration

Extensive, lacy pattern

minor

Epidermis

Normal

Hyperplastic

cells

Small, uniform

Polymorphic

Cellularity

Uniform

Variable

Collagen edge

Normal or fibrotic

Prominent wrapping by cells

Immuno

CD34+, SMA-

CD34-,SMA+

Case10 • 40 M with painful nodule on finger.

Microscopy • Circumscribed tumour • Small cells, very regular with central round dark nuclei and small amount pink cytoplasm.

• Pattern, cords & rings of cells. Often surround blood vessels.

• Prominent blood vessels.

• No ducts.

Glomus Tumour • Differential; Spiradenoma.

• Painful tumours; Glomus, Spiradenoma, pilar leiomyoma,angiolipoma,traumatic neuroma • Modified smooth muscle, SMA positive, desmin negative.

• Glomangiomas, can be multiple and familial.

Case 11 • 62M, Red patch on penis

Microscopy • Scattered cells in epidermis • Show cytological atypia • Scattered cells with vacuole in cytoplasm.

Extra-mammary Pagets • Can be primary skin, presumably of adnexal origin or epidermotropic metastasis.

• Metastases usually from same anatomical region, eg penile check lower urogenital tract.

Differential diagnosis • • • • •

Extra-mammary Paget’s Melanoma Bowen’s Sebaceous carcinoma, esp. Eyelid.

Pagetoid reticulosis.

Special stains/Immunohistochemistry • • • • • • •

ABPAS, Pagets CK 7, Pagets S100 Melanoma LCA P63 Bowen’s PSA/PSAP met. Prostate Ca. CDX2 for Colorectal [CK7 & 20 pos].

Case 12 • 12m Lump on arm

Histological findings • Dense dermal infiltrate mononuclear cells with central nuclei with dispersed chromatin and inconspicuous nucleoli. Delicate nuclear membrane.

• Cells with Central ring of nuclei surrounded by bubbly cytoplasm. Central eosinophilic cytoplasm.

• Some cells with finely vacuolated cytoplasm, especially towards the epidermis.

• Admixed lymphocytes, eosinophils, plasma cells and neutrophils.

Juvenile Xanthogranuloma • Archetypal Xanthogranuloma.

• 2 main clinical forms, papular with numerous small lesions and Nodular with 1 or few nodules.

• Can occasionally be disseminated involving visceral structures.

• Usually undergoes spontaneous regression • Some evidence of clonality. ? involves same genetic loci as Neurofibromatosis

Immunohistochemistry Cells are of monocyte macrophage series with positivity for CD68,CD163 and negative for CD1a and Langerin.

Juvenile Xanthogranuloma 3 stages • Early; Red patch • Classical; Yellow nodule • Late; Indurated ‘burnt out’.

Differential diagnosis • Xanthoma. No Touton cells, inflammatory cells.

• LCH • Dermatofibroma. Can have occ. Touton cells.

Most cells not true histiocytes. No eosinophils.

Characteristic collagen wrapping.

• Spitz naevus.

JXG • There is an association with chronic myloid leukaemia and Neurofibromatosis • Many closely related xanthogranulomatous entities eg spindle cell xanthogranuloma,xanthoma disseminatum, progressive nodular histiocytosis.

Histiocytic disorders • 1]Macrophage disorders of Myeloid derived cells of monocyte-macrophage series. Bone marrow derived. Phagocytic function.

• 2] Dendritic cells of myeloid or stromal derived stem cells. Antigen presenting cells.

Monocyte-macrophage disorders • Benign; – Xanthogranuloma family – Xanthomatous infiltrates – Rosai Dorfman disease

• Malignant – Histiocytic sarcoma

Histiocytic Infiltrates • • • •

Many, many disorders.

Literature confusing.

Focus on few main groups.

Classification of some groups is improving.

Non-Langerhan’s histiocytoses B.Zelger et al, Am.J.Dermpath. 18:490-504, 1996

Non-Langerhan’s Histiocytoses

Case 13 • 20F chronic vulval ulcer

Histological findings • Infiltrate which involves dermis and epidermis.

• Characteristic Langerhans cell [LCH] within infiltrate which are large cells with abundant slightly eosinophilic cytoplasm. They have central nuclei with folded/reniform nuclear membrane.

Nucleus pale with fine chromatin and small indistinct nucleolus.

• Background contains admixture of lymphocytes, eosinophils and sometimes histiocytes of monocyte macrophage series.

Langerhan’s cell histiocytosis • Now well defined. Immunophenotype characteristic being positive for CD1a, s100, and langerin. Negative for CD68, HLA-DR • Different variants characterised by clinical extent of disease.

• Mostly occurs in childhood, but not always.

• Unknown if reactive or neoplastic.

• Clinical course depends upon extent of disease at presentation.

– 99% survival if Unifocal – Significant mortality if multisystem disease.

Case 13 • Imaging revealed bone involvement

Dendritic cell infiltrates • Many types now becoming recognised with use of immunohistochemistry.

Cell of origin for Histiocytic lesions From WHO classification

Case 14 • 85M, Hard nodule on scalp

Microscopy • • • •

Poorly defined ulcerated dermal lesion.

Minor atypia to epidermis.

Prominent collagen deposition Scattered cells with variable spindle to epithelioid morphology. Mild nuclear atypia.

• Occasional mitoses.

Differential diagnosis • • • • •

Hypertrophic scar Desmoplastic melanoma Metastatic carcinoma, especially breast.

Sarcoma Desmoplastic SCC

Desmoplastic SCC • Cytokeratin positive.

• No evidence of disease elsewhere.

• Important to remember to include cytokeratins with spindle cell tumours.

Case 15 • 70F Rapidly growing tumour on scalp

Case 15 • Dermal based squamo-proliferative lesion.

• Cystic component. Squamous cells are large with prominent eosinophilic cytoplasm. Closely packed without prickles.

• Abrupt keratinisation without granular layer or flattening of cells. Central compact keratin.

• Infiltrative margin with a desmoplastic stroma.

• Minimal nuclear atypia.

Differential diagnosis • SCC • Proliferating Tricholemmal Tumour [PTT]

Proliferating Tricholemmal Tumour • Shows differentiation towards outer root sheath at level of follicular isthmus.

• Occurs on scalp of Elderly females.

• Vary from large cyst with proliferation of lining and no nuclear atypia to infiltrative tumours with marked cytological atypia.

Proliferating Tricholemmal Tumour • Controversy on how to classify. Some would split intra -cystic ones [benign] from infiltrative cases [malignant], Others consider all malignant [A.B.Ackerman] Proliferating Tricholemmal cystic carcinoma . In WHO classification placed under malignant.

• Majority behave in a benign fashion but can behave aggressively both locally and with distant spread, but the incidence is unknown.

• ? One type of Tricholemmal carcinoma that can be identified arising from terminal hairs.

Case 16 • 80F wart on wrist

Main histological features • Squamo-proliferative lesion • Small squamous cells, in lobules connected to epidermis.

• Foci with cytological atypia • Focal infiltrative growth pattern.

• Ducts with cuticular lining present.

Differential diagnosis • SCC • Porocarcinoma

Porocarcinoma • Often missed and called SCC. • Has significant mortality rate ;12% • EMA and pCEA useful to identify ductal differentiation.

Case 17 • 67F lump in umbilicus

Main features • Dermal tumour composed of glands and ducts.

• Permeates entire dermis • Mild atypia

Differential diagnosis • Primary adnexal adenocarcinoma • Metastasis

Metastatic adenocarconoma • Sister Mary Joseph’s nodule.

• Adenocarcinoma’s of stomach,colon,ovary,endometrium usual sites • This case was cholangiocarcinoma.

• Often presenting feature.

Case 18 • 70 Male, lump on leg.

Main features • Dermal tumour • Small cells in sheet-like pattern • Cells have little cytoplasm and round nuclei with dispersed chromatin and no nucleoli.

• Mitoses++

Differential diagnosis • • • •

Merkel cell carcinoma Metastatic carcinoma , usually lung.

Lymphoma melanoma

Immunohistochemistry • Cytokeratin positive, often paranuclear dot • Often synaptophysin or chromogranin positive.

• CK 20 positive, N.F. positive and TTF1 negative , useful for distinguishing from lung.

• S100 negative

Interesting points • Associated with Polyoma virus.

• Can be associated with Bowen’s or SCC. • Highly aggressive tumour. 75% get L.N. Mets.

Case 19 • 55 F with tumour on eyelid

Main features • Lakes of Mucin • Islands of epithelial cells. Small cells with only mild atypia.

• Infiltrates through dermis

Differential diagnosis • Primary mucinous carcinoma • Metastatic mucinous carcinoma ; – Breast – Colon

Useful pointers • Mets to skin usually occur in same anatomical zone as primary eg breast to axilla.

• Eyelid common site for primary Mucinous carcinoma.

• Colorectal mets; have dirty necrosis, immuno profile different, CK 7 neg, CK 20 pos [skin mucious CK7 pos, CK 20 neg] • Breast, morphologically and immunohistochemically identical.

Primary Skin Mucinous carcinoma • Look for in-situ disease.

• Immuno for basement membrane or myoepithelial cells can highlight.

Case 20 • 25 male with changing mole on back

Main features • Melanocytic tumour. Juntional component composed of nests.

• Symmetrical, cicumscribed • Dense infiltrate, evenly distributed.

• No marked cytological atypia.

• No dermal mitoses

Halo naevus • • • • • •

Term refers to clinical appearance.

Can affect several naevi. Usually young adults.

Process occurs in an even pattern Cells can appear mildly enlarged.

Can affect dysplastic naevi.

S100 useful to highlight archetecture.

Case 21 • 20 m, odd mole on arm

Main features • • • • •

Papillomatous melanocytic tumour.

Juctional commponent, regular nests.

Dermal component, 2 cell types.

Small regular naevoid cells.

Larger cell with more cytoplasm and pigment.

Combined Naevus Naevi with phenotypic heterogeneity • 2 Cytologically different populations in a single naevus.

• Disobeys rules on symmetry.

• Usually in congenital naevi • Different names in literature describing this phenomenon.

– Atypical dermal nodule – Clonal Naevus – Inverted type A

True and Blue/ Atypical dermal nodule; Pointers • Both components on their own are benign.

• No or minimal nuclear atypia. Large cell component due to cytoplasm.

• No in-situ melanoma. Melanoma arising from dermal component is very rare.

• Mitotic activity very low • 10 year follow up, no disease.

Combined Naevus • Variants.

– Congenital or ordinary and Blue [True and Blue].

– Congenital and Spitz – Spitz and Blue- very difficult

Case 22 • 55 M changing mole on back

Main Features • • • •

Melanocytic tumour Asymmetry Junctional component variable Area with thinnig of epidermis, confluent melanocytes at dermo-epidermal junction.

• Clefting of epidermis from dermis.

Melanoma • Age and clinical important [> 50, sun exposed site].

• Thining and clefting of epidermis helpful.

Case 23 • 35 male with mole on foot

Main features • Predominately junctional. Nests circumscribed.

• Epidermal archecture not effaced.

• Minimal cytological atypia • No lymphoid reaction.

• Some upward epidermal spread.

• If dermal component, bland.

Acral Naevus • Often junctional to later life.

• Still symmetrical etc.

• Can have upward epidermal spread. Not pagetoid as not cytologically atypical.

• Rarely lymphocytic reaction.

• Cytology plays larger role.

Case 24 • 5 F fleshy polyp

Main features • • • •

Polypoid melanocytic lesion Composed of epithelioid melanocytes Does not mature properly.

Cells at deep aspect have visible nucleoli

Atypical spitzoid tumour Features to be wary of; • Age very important. <10 yrs, nearly always benign even when histologically worrying. >50yrs, often malignant even when histologically bland.

• Size, >1cm ,beware • Thin epidermis [consumption].

• Compact nest deep • Abrupt changes • Deep mitoses

Case 25 • 75 Male with pigmented lesion on forehead

Main features • Dermal fibrosis • Perivascular inflammation • Juctional component, single cells and nests of melanocytes.

Desmoplastic melanoma • • • • • •

Watch out for scars on sun damaged skin.

Perivascular lymphocytes a pointer.

Collagen not horizontal.

Neurotopism often present Lentigo maligna frequently present.

If pure, may have better prognosis than melanoma NOS.

Lentigo maligna.

• Useful guide; – Older age, sun damaged skin.

– Melanocytes in epidermis come to lie next to each other, or small nests.

– Cytological atypia – Extension down adnexal structures

Case 26 • 30F Giant congenital naevus, now developed a nodule

Main features • Background of congenital naevus.

• Nodule within compsed of larger cells more compactly arranged.

• Nuclei, regular. Infrequent mitoses.

• No necrosis • No epidermal component

Proliferative nodule in Giant congenital naevus • Dermal based nodule composed of compact larger melanocytes.

• Nuclei, although can be a bit larger than surrounding melanocytes, are not atypical.

• Mitoses rare, no necrosis.

• Vast majority benign.

• Can develop multiple nodules.

Case 27 • 66F, Lesion on temple

Main features • Infiltrative tumour.

• Squamoid cells.

• Gland and duct like spaces

Differential Diagnosis • Porocarcinoma • Metastasis • SCC

Acantholytic SCC • Not true glands. Due to acatholysis.

• Not highlighted by EMA or pCEA. • High risk sub-type of SCC.

Case 28 • 70 m, Lump on scalp

Histopathological features • • • • • •

Architecture Circumscribed with pushing margin Minimal subcutaneous fat extension No vascular invasion No tumour necrosis.

No in-situ disease is present .

Histopathological features • Cytology; tumour cells have high grade atypia with pleomorphic cells, atypical xanthomatous cells and spindle cells in varying proportion.

There are numerous osteoclastic giant cells

Malignant epithelioid tumours • Carcinoma, including metastasis • Melanoma • Sarcoma – LMS – Angiosarcoma

• Lymphoma, anaplastic large cell • AFX

Diagnosis of AFX • Main differential • How to make diagnosis.

Atypical Fibroxanthoma AFX • Elderly, sun damaged sites, esp. head & neck • Raised cutaneous nodule

AFX • Architecture – Circumscribed with pushing margin – Minimal subcutaneous fat extension – No vascular invasion – No Tumour necrosis

AFX • Tumour cell; high grade atypia with pleomorphic cell, atypical xanthomatous cells and spindle cells in varying proportion

AFX • Diagnosis of exclusion; rule out melanoma, carcinoma, sarcoma.

• Exculsion based on archecture and Immunohistochemistry.

• Immuno. Panel; Broad spectrum cytokeratins, S100, Desmin.

• CD10 ? Useful.

AFX • Beware if not sun damaged site • ? Risk if immunosuppressed • If has any aggressive features –’Pleomorphic sarcoma’

AFX Rare variants • • • • •

Osteoclastic giant cell rich Granular cell Clear cell Spindle cell Osteoid/chondroid

AFX • Cell of origin; unknown, but hotly debated.

Case 29 • 30 Female with warty lesion on scalp.

Histological Features • Glandular tumour in dermis.

• Variable tubular, glandular and papillary patterns.

• Cells display apocrine features, abundant eosinophilic cytoplasm and apocrine blebs.

• Nuclear atypia, infiltrative growth pattern.

Apocrine carcinoma • Eccrine and apocrine tumours overlap.

• Problem of separating primary from secondary spread from the breast.

• Breast is modified sweat gland.

Primary Vs metastatic carcinoma [breast] • Immunohistochemistry for different profile unhelpful.

• Look for either In-situ or precursor lesion.

• In-situ disease identified by stains for myoepithelium and basement membrane.

• Precursor lesion in adjacent skin. In this case a Naevus Sebaceous present.

Naevus Sebaceous [Organoid Naevus] • Usually oval lesion on scalp.

• Has 3 ages – Childhood – Hairless oval patch with smooth surface – Teens- Warty/ papillomatous surface – Adults – Tumours arise. Many types described, usually follicular types.

Case 30 • 40 Male with ? Cyst on finger

Histological findings • Multinodular deep dermal tumour on distal extremities.

• Nodules composed of back-back glands with central cystic space.

• Broad papillae composed of heaped up cells are present.

• Mitoses are frequent. Often only mild nuclear atypia.

• Necrosis often present .

• Border can be infiltrative or circumscribed.

• No distinct immunoprofile

Digital Papillary Carcinoma • Occurs on extremities, particularly fingers and toes.

• Mid-age adults with cyst /lump +/-painful.

• Frequent local recurrance unless radical excision eg amputation.

• Metastasizes in 15%

Problem areas • Benign versus malignant – At lower end of spectrum, originally called adenoma and carcinoma based on histological features. Longer follow up shown all can behave in malignant fashion, therefore all called malignant in WHO classification.

Differential diagnosis • Mimic a metastasis from visceral site.

• Papillary eccrine adenoma – Circumscribed.

– Cysts contain delicate papillae with 2 cell layer.

– Lacks back to back glands/ mitoses and heaped up cells forming papillae.

THE END • BEST OF LUCK