Skin-tumor

Last revised 18 May 2008

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Table of Contents Skin-tumor

Primary references

Benign (nonmelanotic) epidermal tumors or tumor-like lesions: clear cell papulosis, cutaneous horn, fibroepithelial polyp, large cell acanthoma, melanoacanthoma, pseudoepitheliomatous hyperplasia, seborrheic keratosis, verrucous hyperplasia

Cysts: apocrine cystadenoma, bronchogenic cyst, cystadenoma, dermoid cyst, hidrocystoma, keratinous cyst, pigmented follicular cyst, steatocystoma, vellous hair cyst

 

Adnexal tumors: general

Apocrine glands: general, apocrine tubular adenoma, hidradenoma papilliferum

Eccrine sweat glands: acrosyringeal adenomatosis, aggressive digital papillary adenoma, chondroid syringoma, clear cell acanthoma, cutaneous lymphadenoma, eccrine acrospiroma, eccrine cylindroma, eccrine poroma, eccrine spiradenoma, intraepidermal epithelioma, mucinous carcinoma, myoepithelioma, papillary eccrine adenoma, papillary syringadenoma, sclerosing sweat duct carcinoma, sweat gland carcinoma, syringoma

Hair follicles: folliculofibroma, inverted follicular keratosis, keratinous cyst, keratoacanthoma, pilar tumor, pilomatrixoma, trichilemmoma, trichoepithelioma, trichofolliculoma, warty dyskeratoma

Sebaceous glands: nevus sebaceous of Jadassohn, sebaceous adenoma, sebaceous carcinoma, senile sebaceous hyperplasia

 

Premalignant/in situ: carcinoma in situ-general, actinic keratosis, bowenoid papulosis, Bowen’s disease, Paget’s disease

Carcinoma (non adnexal): adenoid cystic carcinoma, adenoid squamous cell, adenosquamous, basal cell, lymphoepithelioma-like, Merkel cell, metastatic, mucoepidermoid, small cell, spindle squamous cell, squamous cell, verrucous carcinoma, staging

 

Nevi: general, active, balloon cell, Becker’s, blue, cockarde, combined, compound, congenital, dermal, dysplastic, halo, Ito’s, junctional, lentiginous, Mongolian spot, Ota’s, Spitz, Sun’s

Melanoma: general, desmoplastic, minimal deviation, pigmented epithelioid melanocytoma, sentinel node biopsy, Breslow, Clark’s levels, features to report, staging

Other melanocytic lesions: general, atypical melanocytic hyperplasia, café-au-lait spot, ephelis, hyperpigmentation, paraganglioma-like dermal melanocytic tumor, solar lentigo, vitiligo

 

Lymphoma and related disorders: general, acute lymphoblastic, anaplastic large cell, angiocentric, blastic NK leukemia / lymphoma, diffuse large B cell, follicular, Hodgkin’s, HTLV-1, intravascular, Jessner’s lymphocytic infiltration of skin, leukemia, lymphoid hyperplasia, lymphomatoid papulosis, mantle zone, mast cell disorders, mycosis fungoides, NK/T cell, peripheral T cell, primary cutaneous (general), Woringer-Kolopp disease

Vascular tumors: acquired angioma, angiosarcoma, bacillary angiomatosis, benign hemangioendothelioma, benign lymphangioendothelioma, glomus, hemangioma, hemangioendothelioma and subtypes, intravascular papillary endothelial hyperplasia, Kaposi’s sarcoma, Kimura’s disease, lymphangioma, pyogenic granuloma, reactive angioendotheliomatosis, vascular leiomyoma, verruga peruana

Other tumors of skin: angiofibroma, atypical fibroxanthoma, benign cystic teratoma, benign fibrous histiocytoma, collagenous fibroma, dermatofibrosarcoma protuberans, dermatomyofibroma, endometriosis, epithelial sheath neuroma, granular cell tumor, hamartoma of scalp, histiocytoma, inclusion body fibromatosis, inflammatory pseudotumor, keloid, Langerhans cell histiocytosis, leiomyoma, leiomyosarcoma, malignant fibrous histiocytoma, malignant peripheral nerve sheath tumor, meningioma, meningioma-like tumor of skin, neurofibroma, neurothekeoma, palisaded encapsulated neuroma, perineurioma, pleomorphic fibroma, schwannoma, sclerosing fibroma, sinus histiocytosis with massive lymphadenopathy, striated muscle hamartoma, supernumerary digit, xanthoma, xanthogranuloma

 

Go to Skin-nontumor chapter

 

Primary references

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AJCC Cancer Staging Manual (6th Ed)

American Journal of Surgical Pathology (AJSP), January 2003 to February 2005

Archives of Pathology and Laboratory Medicine (Archives), Jan 2005 to February 2005 (must do cutaneous)

Human Pathology (Hum Path), Feb 2004 to December 2004 (must do cutaneous)

Modern Pathology (Mod Path), Jan 2003 to January 2005 (must do cutaneous)

Rosai, J: Ackerman’s Surgical Pathology (9th Ed); 2004

Sternberg, S: Diagnostic Surgical Pathology (4th Ed); Lippincott Williams & Wilkins, 2004

Journal search terms: skin, epidermis, dermis, cutaneous

 

 

Benign nonmelanotic epidermal tumors / tumor-like lesions

Clear cell papulosis

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Children 0-3 years

Gross: small white maculopapular lesions

Micro: large pale cells (Toker’s cells), single or in clusters

Positive stains: CEA, EMA, low molecular weight keratin

DD: Paget’s disease

 

Cutaneous horn

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Also called cornu cutaneum

Usually caused by actinic keratosis, also verruca, seborrheic keratosis, inverted follicular keratosis, squamous cell carcinoma

Gross: protruding skin lesion composed or keratin and resembling a horn

Micro: usually epidermal type keratin (with granular layer); occasionally has trichilemmoma-like features (no granular layer but deep red granules)

 

Fibroepithelial polyp

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Also called acrochordon, squamous papilloma, skin tag, soft fibroma

Common, non-neoplastic, no clinical significance

Ages 40+ years; usually face, neck, trunk, intertriginous areas

Associated with diabetes, intestinal polyposis; increase during pregnancy

May be a common endpoint of various processes, including seborrheic keratosis or warts

Acquired (digital) fibrokeratoma: collagenous protrusions covered by hyperkeratotic epithelium, often at interphalangeal joints; dermis lacks adnexae

Gross: soft, flesh-colored, baglike tumor, attached to skin by slender stalk

Micro: papillary, fibrovascular cores covered by squamous epithelium; may have ischemic necrosis due to torsion

 

Large cell acanthoma

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Sun exposed skin, usually cheek or forehead

Benign, although may be related to actinic keratosis

Gross: light-tan to dark brown macule

Micro: atrophic, acanthotic or verrucous epidermis; hyperpigmented basal layer with rounded contour of rete ridges; larger than usual keratinocytes (large nuclei and cytoplasm) compared to adjacent normal epidermis; no atypia

 

Melanoacanthoma

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May be a pigmented variant of seborrheic keratosis

Benign

Micro: resembles seborrheic keratosis but with prominent, dendritic melanocytes with abundant melanin granules; melanocytes are scattered throughout the lesion; no atypia

 

Pseudoepitheliomatous hyperplasia

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Due to reparative changes associated with ulcer, trauma, chronic irritation, North American blastomycosis, tuberculosis, syphilis, granular cell tumor, Spitz nevi, melanoma

Micro: deep tongues of epithelial cells that may appear invasive but are thin, elongated, anastomosing and surrounded by inflammatory cells (acute/subacute); also dermal fibrosis and vascular proliferation; no/rare atypia

DD: squamous cell carcinoma (thicker strands, atypia, usually no prominent inflammatory infiltrate)

 

Seborrheic keratosis

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Common; usually age 40+ years

Benign, although may coexist with malignancy

Usually affects trunk, head and neck, extremities; only hair bearing skin

Not HPV related, although HPV present in morphologically similar cases of epidermodysplasia verruciformis and bowenoid changes

Dermatosis papulosa nigra: in blacks

Leser-Trelat sign: sudden appearance or increase in number and size of seborrheic keratoses, associated with internal malignancy

Treatment: superficial curettage, freezing

Gross: exophytic, sharply demarcated, pigmented lesions that protrude above surface of skin, appear to be stuck to skin, single or multiple, soft, tan-black

Micro: basal keratinocyte proliferations

Patterns: acanthotic – most common, rounded verrucous surface; thick layer of basal cells mixed with horn cysts (contain keratin) and pseudohorn cysts (downgrowth of keratin into tumor mass); no prominent granular layer; some cells contain melanin due to transfer from neighboring melanocytes

irritated – pronounced squamous metaplasia with abundant eosinophilic cytoplasm and whorled squamous eddies; often atypia and mitotic figures; resembles carcinoma

inverted follicular keratosis – irritated seborrheic keratosis that grows downward and involves hair follicles

Also hyperkeratotic, adenoid, acantholytic and desmoplastic patterns

Positive stains: low molecular weight keratin

Negative stains: high molecular weight keratin (usually), HPV

DD: squamous cell carcinoma (particularly desmoplastic pattern)

 

Verrucous hyperplasia

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Papillomatosis associated with hyperkeratosis

Benign

Nonspecific change, associated with various entities

Epidermal nevus: if present since birth or early childhood; higher risk for basal cell carcinoma or adnexal tumors

Nevus sebaceous of Jadassohn: associated with malformed adnexal structures (see below)

Verruca vulgaris: exophytic growth with marked hyperkeratosis, focal parakeratosis, papillomatosis resembling church spires, prominent granular layer, koilocytosis, dilated vessels within papillary dermis

 

 

Cysts

Apocrine cystadenoma

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Usually face, solitary or multiple

Lined by sweat duct-like epithelium which may have apocrine features

 

Bronchogenic cyst

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Lesion of suprasternal notch, discovered shortly after birth

Probably derived from branchial clefts, not bronchi

Micro: lined by bronchial (pseudostratified, ciliated columnar) epithelium

 

Cystadenoma

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Also called cutaneous ciliated cyst

Usually extremities of teenage girls

May have mullerian derivation, although rarely described in males

Micro: cylindrical cells with cilia

 

Dermoid cyst

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Resemble keratinous cysts of epidermal type, but also have hair adnexae

Usually face of children along embryonic closure lines

 

Hidrocystoma

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Usually face, solitary or multiple

Lined by two rows of sweat duct-like epithelium which may have apocrine features

 

Keratinous cyst

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See below

 

Pigmented follicular cyst

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Hyperpigmented lesion with epidermal-type keratinization, contains laminated keratin, pigmented hair shafts, some growing hair follicles

 

Steatocystoma

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Solitary (simplex, often scrotal) or disseminated (steatocytoma multiplex, autosomal dominant, dermal nodules 1-3 mm of upper arms, axilla, scrotum and presternal skin)

Gross: cysts contain clear fluid

Micro: cyst with elaborate inner folding of cyst wall with undulations of thin layer of stratified squamous epithelium resembling ductal portion of sebaceous gland; also lobules of sebaceous glands and small hair follicles

 

Vellous hair cyst

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Children and young adults

Small, multiple cysts over chest wall and extremities

Micro: cyst lined by flattened, follicular sheath epithelium; contains numerous vellous hairs and soft keratinous material in lumen

 

 

Adnexal tumors

Adnexal tumors-general

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Usually differentiate only along one adnexal line, but there may be divergent differentiation within 1 or more tumors within the same patient

Algorithms (from Sternberg)

Cystic lesions:

(a) glandular lesions are hidrocystoma (two rows of cells) or cutaneous ciliated cyst (cylindrical cells with cilia)

(b) lesions with squamous keratinization are trichilemmal cysts, pilomatricoma, steatocytoma (sebaceous lobules in wall), vellous hair cyst (hair shafts in lumen), epidermoid cyst (contains lamellated keratin), dermoid cyst (adnexal structures in wall), trichofolliculoma (radiating immature hairs) or warty dyskeratoma (acantholytic dyskeratosis)

Basaloid tumors:

Trichoepithelioma / trichoblastoma (ribbons of basaloid cells, cysts and fibroblastic stroma), trichofolliculoma (mature and immature hair follicles), cylindroma (jigsaw-puzzle appearance with thickened basement membrane), spiradenoma (basaloid cells with 2 cell types), sebaceous adenoma or carcinoma, eccrine poroma (large nodules connected to epidermis), eccrine acrospiroma (large dermal nodules), pilomatricoma (ghost cells)

Squamoid tumors:

(a) solid lobules of eosinophilic cells are pilar sheath acanthoma (connected to crater-like cavity) or acrospiroma (not connected to crater-like cavity)

(b) lobules with clear cells are acrospiroma (luminal differentiation), trichilemmoma (epidermal connection, peripheral palisading, thick basement membrane) or sebaceous tumors

(c) lobules of squamous cells with central keratinization are proliferative trichilemmal tumor

Glandular tumors:

(a) apocrine differentiation: papillary hydradenoma (papillary fronds, vulvar/perianal) or tubular apocrine adenoma (epidermal connection)

(b) syringoma: small ducts with 2 rows of cells

(c) papillary eccrine adenoma: cystic ducts and papillary fronds

(d) papillated ducts open to epidermis: papillary syringadenoma (scalp) or nipple adenomatosis (nipple)

(e) mixed tumor (chondroid syringoma): chondromyxoid stroma and tubular or anastomosing glands

(f) sebaceous hyperplasia (lobular arrangement around a central duct), adenoma or carcinoma

 

 

Adnexal tumors-apocrine glands

Adnexal tumors of apocrine glands - general

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Eccrine sweat gland tumors may exhibit apocrine differentiation

Pure apocrine tumors are rare

 

Apocrine tubular adenoma

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Micro: lobular pattern of dermal and subcutaneous tubular apocrine structures with epidermal connection; resembles papillary syringadenoma

 

Hidradenoma papilliferum

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Also called papillary hydradenoma

Perianal or vulvar

Micro: papillary fronds, ducts lined by apocrine type cells which show decapitation secretion and fibrous stroma

 

 

Adnexal tumors-eccrine sweat glands

Acrosyringeal adenomatosis

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Also called eccrine syringofibroadenoma

Gradual and symmetric spread of papular lesions over large areas of body

Micro: diffuse proliferation of acrosyringium-related cells in epidermis and dermis

 

Aggressive digital papillary adenoma

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Usually digits

Recurs locally

Malignant counterpart has poor glandular differentiation, necrosis, atypia, invasion; metastasizes to lung in many cases

Micro: tubuloalveolar and ductal structures, also areas of papillary projections protruding into lumina (may resemble breast carcinoma)

 

Chondroid syringoma

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Also known as mixed tumor of skin

Usually benign

Face, head, neck, extremities, trunk or back

May have areas of apocrine, follicular and sebaceous differentiation

Gross: nodular, circumscribed, nonulcerated

Micro: myoepithelial and epithelial type cells, some with abundant hyaline cytoplasm, in chrondomyxoid stroma; may have eosinophilic globules with radiating fibrillary structures around their lumina, similar to mammary collagenous spherulosis

Positive stains: inner epithelial layer - keratin, EMA, CEA; outer myoepithelial layer – vimentin, S100, NSE; variable smooth muscle actin, GFAP

 

Apocrine mixed tumors

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Epithelial component is branching tubular structures with two cell layers; inner layer is columnar with eosinophilic cytoplasm, “decapitation” type secretion, often squamous metaplasia and basal nuclei

 

Clear cell acanthoma

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Legs of females, may be multiple

Acanthoma: benign tumor of epidermal keratinocytes

Gross: moist flat plaque

Micro: intraepithelial tumor of clear keratinocytes with dermal inflammation and abrupt transition to normal epidermis; may have melanocytic proliferation, psoriasiform acanthosis, parakeratosis

Positive stains: glycogen

DD: seborrheic keratosis

 

Cutaneous lymphadenoma

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May be related to eccrine spiradenoma

Micro: multiple rounded lobules of basaloid cells with some peripheral palisading, focal keratinization, occasional duct formation, mixed with small lymphocytes

 

Eccrine acrospiroma

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Also called solid-cystic or nodular hidradenoma

Arises from sweat gland distal excretory duct

Gross: nodules with cystic foci high in dermis

Micro: nests/lobules of cells resembling eccrine poroma with either clear cytoplasm or prominent squamous metaplasia; may have marked vascularity

Positive stains: keratin, EMA, CEA, S100, vimentin

DD: glomus tumor (different staining pattern)

 

Eccrine cylindroma

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Also called turban tumor, particularly when a large, multicentric scalp tumor

Somewhat common; solitary, small, slow growing adenoma, 90% in head and neck

Usually ages 40+ years, 90% women

Rarely associated with similar tumors in major salivary glands

Familial form (turban tumor syndrome, Brooke-Spiegler syndrome): autosomal dominant, multiple tumors of children / teenagers that may also involve trunk and extremities, or in association with spiradenoma, trichoepithelioma, milia or membranous variant of basal cell adenoma of salivary glands; due to mutations in CYLD gene at #16q12-13

Rarely undergoes malignant transformation

Spiradenocylindromas: features of cylindroma and eccrine spiradenoma; usually painful

Gross: pink-red dome-shaped nodule with smooth surface

Micro: compact nests of basaloid cells that fit together like a jigsaw puzzle, surrounded by thick basement membrane

Molecular: mutation in CYLD gene in #16 associated with multiple cylindromas

EM: differentiation towards intradermal coiled duct region of eccrine sweat glands

 

Eccrine poroma

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Palms and soles, also other sites

Benign, although eccrine porocarcinomas also exist

May be a subtype of eccrine acrospiroma

Gross: “moat and hillock” pattern

Micro: cords and nests of small keratinocytes attached to the epidermis; nests are sharply delimited from adjacent epidermis; also ducts and sharply delimited islands of squamous epithelium; either intraepidermal (“hydroacanthoma simplex”), intradermal (“dermal duct tumor”) or mixed (most common); dermis has reactive vessels and inflammatory infiltrate; also heavily pigmented variants

Positive stains: EMA

EM: features of eccrine gland acrosyringium

DD: basal cell carcinoma, seborrheic keratosis, acrosyringeal adenomatosis

 

Malignant eccrine poroma

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Also called porocarcinoma

Most common sweat gland carcinoma

Usually lower extremities, may be pedunculated

Recurs locally, also metastasizes to regional lymph nodes

Micro: malignant eosinophilic and clear cells in lobular masses or islands with cystic cavities due to extensive necrosis; eosinophilic cells are polyhedral or fusiform with variable cytoplasm, hyperchromatic nuclei, distinct nucleoli, indistinct cell boundaries; clear cells are large and polyhedral with abundant clear cytoplasm and distinct cell borders; resembles eccrine poroma, but with obvious atypia and frequent mitotic figures; also epidermotropism resembling Paget’s disease; variable squamous differentiation, clear cell change and pigmentation

Either horizontal pattern (intraepidermal, like superficial spreading melanoma) or nodular (into dermis, like nodular melanoma)

DD for horizontal pattern: intraepidermal poroma (no atypia), seborrheic keratosis (no atypia), Bowen’s disease (more atypical keratinocytes, more severe architectural abnormalities), Paget’s disease (large cells, clear cytoplasm, mucin+)

DD for nodular pattern: squamous cell carcinoma (prominent keratinization, keratin pearls, no cystic cavities), sebaceous carcinoma (clear cells with bubbly cytoplasm), proliferating trichilemmal tumors (solid and cystic, well demarcated with palisading of peripheral layer), metastatic renal cell or other clear cell tumors, balloon cell melanoma

 

Eccrine spiradenoma

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Extremely painful lesions, anywhere in body

Rarely transforms to high grade malignancy

Micro: sharply circumscribed, lobular adenomas; very cellular; cells have scant cytoplasm; high vascularity; variable T cells

Micro images: contributed by Dr. Amy Lynn, Toledo, Ohio - image

EM: epithelial and myoepithelial cells

DD: synovial sarcoma, metastatic carcinoma, thymoma, cutaneous lymphadenoma

 

Intraepidermal epithelioma of Borst-Jadassohn

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Heterogeneous group of disorders, including irritated seborrheic keratosis, eccrine poroma and other intraepidermal sweat gland tumors

 

Mucinous carcinoma

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Also called adenocystic carcinoma

Scalp of elderly patients

Micro: resembles mammary colloid carcinoma with lakes of mucin containing small tumor cell clusters; may also have an infiltrating ductal pattern

DD: metastatic carcinoma

 

Myoepithelioma

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Tumors with myoepithelial cells but no epithelial cells

Usually benign lesions of extremities, but should be completely excised

May recur locally, rarely metastasize

Usually male, mean age 22 years (range 10-63 years)

Part of a continuum with mixed tumors (ductal structures but few myoepithelial cells)

Mitotic activity may predict more aggressive tumor

Gross: mean 1 cm, range 0.5 to 2.5 cm

Micro: well circumscribed dermal lesions, not connected to epidermis, may extend into superficial subcutis; either composed of (a) solid proliferation of ovid, spindled, histiocytoid or epithelioid cells with abundant eosinophilic syncytial cytoplasm and little stroma; or (b) reticular architecture with epithelioid, plasmacytoid or spindle cells in myxoid or hyalinized stroma; cells have ovoid/spindled nuclei, mild pleomorphism, small necrotic areas, fatty metaplasia, minimal mitotic figures (0-6/10 HPF), no ductal differentiation

Positive stains: required for diagnosis by Fletcher - (a) EMA+ or keratin+ and (b) S100 and (c) GFAP (50%) or muscle markers calponin, smooth muscle actin (57%) or muscle specific actin (HHF)

DD: benign mixed tumor, epithelioid benign fibrous histiocytoma (lower limbs, circumscribed, polypoid, plump and often binucleate epithelioid cells, may entrap dermal collagen, keratin-, myogenic markers-, S100-), Spitz nevus (large epithelioid melanocytes with prominent nucleoli, junctional component, downward maturation, HMB45+, S100+, EMA-, keratin-, myogenic markers-), epithelioid sarcoma (distal extremities of young adults, infiltrates along fibrous septa and fascial planes, discontinuous growth, S100-, GFAP-), cellular neurothekeoma (nested architecture, sclerotic dermal collagen, NKI-C3+, S100-, EMA-, keratin-), leiomyoma

References: Hum Path 2004;35:14

 

Myoepithelial carcinoma

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Severe cytologic atypia and high mitotic rate

 

Papillary eccrine adenoma

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Usually distal extremities of blacks

Recur locally, don’t metastasize

Micro: eccrine duct-like structures, often dilated and with intraluminal papillomatosis

EM: differentiation towards secretory epithelium of sweat glands

DD: low grade eccrine carcinoma

 

Papillary syringadenoma

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Warty tumor of scalp, neck and face

Any age

Slow growing or a recent change in an apparent birthmark

1/3 have adjacent nevus sebaceous, 10% have adjacent basal cell carcinoma

Eccrine syringofibroadenoma: with prominent fibrous stroma

Syringocystadenocarcinoma papilliferum: malignant counterpart

Micro: glandular papillary proliferation connected to skin surface, dense plasma cell infiltrate

Positive stains: plasma cells are IgA+, IgG+

 

Sclerosing sweat duct carcinoma

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Also called microcystic adnexal carcinoma

Slow growing nodule or plaque, usually on upper lip or face

Commonly recurs, metastases very rare

Micro: cords and nests of bland keratinocytes, keratin cysts and ductal differentiation; dense collagenous stroma; is invasive, may extend into subcutis or perineurial spaces; resembles syringoma; rarely is sebaceous differentiation

 

Sweat gland carcinoma

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Uncommon

Usually adults

Difficult to diagnose; may be life threatening

Low grade: microcystic carcinoma, adenoid cystic carcinoma, mucinous carcinoma, extramammary Paget’s disease, mucoepidermoid carcinoma

Intermediate grade: ductal adenocarcinoma, aggressive digital papillary adenocarcinoma, acrospirocarcinoma

High grade: porocarcinoma, clear cell acrospirocarcinoma

Unknown grade: signet ring cell carcinoma, papillary syringadenocarcinoma

Includes malignant eccrine poroma (most common), mucinous carcinoma, sclerosing sweat duct carcinoma; also malignant chondroid syringoma (malignant mixed tumor), malignant myoepithelioma, malignant dermal cylindroma, malignant syringoma (syringoid eccrine carcinoma), malignant acrospiroma, aggressive digital papillary adenocarcinoma, apocrine carcinoma, adenoid cystic carcinoma, mucinous syringometaplasia

Benign sweat gland tumors can also undergo malignant transformation to high grade carcinoma

Micro: may resemble breast carcinoma, renal cell carcinoma, basal cell carcinoma

Positive stains: GCDFP-15, estrogen receptor, keratin, EMA, CEA

Negative stains : actin

DD: metastatic breast carcinoma, renal cell carcinoma

 

Syringoma

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Multiple, yellow, papulonodular lesions on lower eyelids of women

Also face and neck, vulva, dorsal proximal and middle phalanges of hand or eruptive forms (below)

Appears to derive from sweat duct ridge

Micro: upper dermal clusters of small ducts lined by two layer thick epithelium, occasionally with comma shaped extensions; may have clear cells (due to glycogen); not infiltrative, no atypia, no mitotic figures, no local destruction

EM: eccrine origin

DD: basal cell carcinoma

 

Eruptive syringoma

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Neck, anterior trunk, axilla, shoulder, anterior surfaces of arms, abdomen or pubic areas of young men or women

May be reactive, not neoplastic

 

Syringomatous carcinoma

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Infiltrative epithelial tumors resembling syringomas

Micro: tubules, keratinizing cystic structures, islands and cords within desmoplastic stroma; involve epidermis and diffusely infiltrates dermis

DD: syringoma (usually multiple, limited to upper dermis, not infiltrative, no atypia, no mitoses, no local destruction), syringomatous carcinoma of salivary glands (in oral mucosa not skin)

 

 

Adnexal tumors-hair follicles

See also cysts (above)

 

Folliculofibroma

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Associated with Birt-Hogg-Dube’ (BHD) syndrome (autosomal dominant, multiple folliculomas on head and neck, acrocordons and trichodiscomas; also renal cell carcinoma [various types], renal oncocytoma and oncocytic hybrid tumors, lung cysts and spontaneous pneumothorax)

Human gene at 17p11.2 encodes folliculin, normally expressed in skin and adnexae; frameshift mutations occur in BHD causing premature protein termination

Tumor considered a hamartoma of hair follicle

Gross: skin papules

Micro: thin epidermal strands originating from a central hair follicle with prominent connective tissue

References: Mod Path 2004;17:998 (mRNA expression of Birt-Hogg-Dube’ mRNA)

 

Inverted follicular keratosis

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Eyelid or face of elderly

May be irritated seborrheic keratosis, irritated verruca vulgaris or keratotic lesion of infundibular region of hair follicle

Gross: single nodule or papule projecting above skin surface

Micro: well circumscribed with squamous eddies containing an inverted papillomatous and acanthotic component; no inflammation

 

Keratinous cyst

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Most probably arise from infundibular portion of hair follicles

Clinically called (incorrectly) sebaceous cyst

Lesions of palm, sole or other sites may contain HPV 57 or 60

Cysts contain keratin and lipid debris from sebaceous secretions

Cysts may be painful if ruptured

Epidermal (epidermoid) type: also called infundibular cyst; lined by keratinized epithelium with distinct granular layer, contain lamellated keratin but no calcification; may have seborrheic keratosis-like changes in cyst wall

Trichilemmal (pilar) type: also called isthmus-catagen cyst; often on scalp, has trichilemmal-type keratinization (sudden keratinization without a granular layer), uneven boundary between keratinized and non-keratinized cells; non-lamellated keratin within the cyst, often with nucleated cells, often calcified

 

Keratoacanthoma

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May represent proliferation of infundibular portion of hair follicle (since keratinization occurs without a granular cell layer), or a subtype of well differentiated squamous cell carcinoma

80% males, usually sun exposed skin of face; younger age group than squamous cell carcinoma of skin

Familial cases may be multiple