Skin nonmelanocytic tumor
Adnexal tumors
Sweat gland derived (apocrine & eccrine glands)

Topic Completed: 1 June 2012

Minor changes: 16 October 2020

Copyright: 2002-2020,, Inc.

PubMed Search: poroma

Christopher S. Hale, M.D.
Page views in 2019: 28,983
Page views in 2020 to date: 21,657
Cite this page: Hale CS. Poroma. website. Accessed October 29th, 2020.
Definition / general
  • Palms and soles, also other sites
  • Benign, although eccrine porocarcinomas also exist
  • May be a subtype of eccrine acrospiroma

Malignant eccrine poroma
  • Also called porocarcinoma
  • Most common sweat gland carcinoma
  • Usually lower extremities, may be pedunculated
  • Recurs locally, also metastasizes to regional lymph nodes
Case reports

Malignant eccrine poroma
Gross description
  • Sessile or slightly pedunculated nodule with normal or erythematous color, firm consistency
  • May ulcerate at points of pressure
Microscopic (histologic) description
  • 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

Malignant eccrine poroma
  • 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)
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Joel Pinczewski, M.D., Ph.D., Australia

Dermal duct tumor

Images hosted on other servers:

Eccrine poroma

Malignant eccrine poroma - High grade tumor invades dermis and subcutis

Eccrine poroma

Positive stains
Electron microscopy description
  • Features of eccrine gland acrosyringium
Differential diagnosis

Malignant eccrine poroma - 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+

Malignant eccrine poroma - 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
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