Skin nonmelanocytic tumor
Adnexal tumors
Sweat gland derived (apocrine & eccrine glands)
Poroma
Author: Christopher S. Hale, M.D.
Topic Completed: 1 June 2012
Minor changes: 16 October 2020
Copyright: 2002-2020, PathologyOutlines.com, Inc.
PubMed Search: poroma
Table of Contents
Definition / general | Case reports | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Electron microscopy description | Differential diagnosisCite this page: Hale CS. Poroma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticeccrineporoma.html. 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
- 64 year old man with poromatosis (Dermatol Online J 2008;14:3)
Malignant eccrine poroma
- 44 year old man (Ann Dermatol 2011;23:S79)
- 56 year old man (Dermatol Online J 2005;11:17)
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
