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


Topic Completed: 1 June 2012

Minor changes: 22 January 2021

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PubMed Search: poroma

Christopher S. Hale, M.D.
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Cite this page: Hale CS. Poroma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticeccrineporoma.html. Accessed March 6th, 2021.
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

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

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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