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Skin - Nonmelanocytic tumors

Adnexal tumors - eccrine sweat glands

Eccrine poroma


Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 5 July 2012, last major update June 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Palms and soles, also other sites
● Benign, although eccrine porocarcinomas also exist
● May be a subtype of eccrine acrospiroma

Case reports
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● 64 year old man with poromatosis (Dermatol Online J 2008;14:3)

Clinical images
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Fig. 1 Pink colored, elongated verrucous plaque on the back of the left thigh.

Gross description
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● Sessile or slightly pedunculated nodule with normal or erythematous color, firm consistency
● May ulcerate at points of pressure

Micro description
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● 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 (“hidroacanthoma simplex”), intradermal (“dermal duct tumor”) or mixed (most common)
● Dermis has reactive vessels and inflammatory infiltrate
● Also heavily pigmented variants

Micro images
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Eccrine poroma

Positive stains
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● EMA

Electron microscopy description
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● Features of eccrine gland acrosyringium

Differential diagnosis
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● Basal cell carcinoma
● Seborrheic keratosis
● Acrosyringeal adenomatosis


Malignant eccrine poroma

General
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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

Case reports
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● 44 year-old man (Ann Dermatol 2011;23:S79)
● 56 year old man (Dermatol Online J 2005;11:17)

Micro description
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● 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)

Micro images
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High grade tumor invades dermis and subcutis

Differential diagnosis
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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

End of Skin - Nonmelanocytic tumors > Adnexal tumors - eccrine sweat glands > Eccrine poroma


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