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Pathology of Eccrine Porocarcinoma

Dr Sampurna Roy MD     



Eccrine porocarcinoma is a rare cutaneous malignancy that arises from the intraepidermal ductal portion of the eccrine sweat gland (acrosyringium).

It was first described, in 1963, by Pinkus and Mehregan as 'epidermotropic eccrine carcinoma' and probably represents the commonest form of sweat gland carcinoma.

The name was coined by Mishima and Morioka in 1969.

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Eccrine porocarcinoma may arise denovo , however some tumours are of long duration suggesting malignant transformation of a poroma or hidroacanthoma simplex. ( Hidroacanthoma simplex is a benign eccrine tumor that is also known as intraepidermal poroma.)

Age:  There is a predilection for older patients and it is often seen during the sixth to eighth decades of life.

Sex: It occurs in both sexes.

Site: Usually located on distal extremities (44%), followed by the trunk (24%), head (18%), upper limbs (11%), and neck (3%).

Clinical presentation: The patient may have a long history of the lesion being present, sometimes up to 50 years. A rapid development of the lesion may occur over a few months.

Presents as a verrucous plaque or polypoid growth which may ulcerate or bleed on trauma .

Microscopic features:

- In the primary tumor, the malignant cells arise from the intraepidermal portion of the eccrine sweat glands and may be limited to the epidermis or may extend into the dermis;

- The tumour is asymmetrical with an infiltrative growth pattern  ; 

- Infiltrating tumour shows multiple attachments to the epidermis ;

- Two types of atypical cells: eosinophilic and clear cells.

Eosinophilic cells- polyhedral or fusiform with round to oval hyperchromatic nuclei, distinct nucleoli, indistinct cell boundaries, and a variable amount of cytoplasm (small eosinophilic cells or large eosinophilic cells); 

Clear cells- large and polyhedral with round to oval nuclei, abundant clear cytoplasm, and distinct cell borders; Clear cell areas are less prominent than hidradenocarcinoma 

- Obvious nuclear atypia with frequent mitoses and focal necrosis (comedonecrosis) are characteristic features;

- Cords and nests of polygonal tumour cells penetrate to the adjacent dermis or extend into subcutaneous tissue ;

- Ductal structures are present with intracytoplasmic lumina formation ;

- Although glandular differentiation is characteristic, poorly differentiated eccrine porocarcinoma may not show obvious duct formations ;

- There is squamous differentiation ;

- Melanin pigment is demonstrated in some cases ;

- Inflammatory infiltrate around neoplastic masses is composed of lymphocytes and plasma cells, rarely mixed with neutrophils and eosinophils ;

- Tumour with only intra-epidermal component is known as in-situ porocarcinoma ;

- Intraepidermal portion of the growth is composed of large atypical cells arranged in irregular nests and islands, variable in size and in shape, and sharply demarcated from the surrounding epidermal keratinocytes ;

Benign component of poroma and hidroacanthoma simplex is present in about 10% of cases.

Neoplastic cells contain glycogen and intratubular, PAS-positive, diastase-resistant material is usually present.

Differential diagnosis:

Histopathologically, basal cell carcinoma, Paget's disease, melanoma, metastatic adenocarcinoma, trabecular carcinoma, and Merkel cell carcinoma should be included in the differential diagnosis.

Distinguishing eccrine porocarcinoma from metastatic adenocarcinoma, and especially adenocarcinoma of a breast or lung origin, can be difficult.

Trabecular carcinoma and Merkel cell carcinoma also show findings comparable with EPC.

Hyperchromatic, large, and irregular nuclei arranged in cord or trabecular patterns are common features of eccrine porocarcinoma and trabecular carcinoma; however, the latter shows nuclear molding.

On immunoperoxidase studies, EMA and CK-7 are positive, and S-100 protein and CK-20 are negative in eccrne porocarcinoma.  

Merkel cell carcinomas express neuron-specific enolase (NSE) and CK-20, and they do not express CK-7.

Immunocytochemistry:  Tumour is cytokeratin , CEA and epithelial membrane antigen positive.

Eccrine porocarcinoma tends to be localized. Local recurrence rate is lower than some low grade tumour.

Metastasis to local lymphnode may be present in 10-20% of cases.

Multiple cutaneous deposits and microscopic epidermotropic deposits may develop.

Distant visceral metastases to the lung, retroperitoneum, long bones, breast, liver, mediastinum, urinary bladder, and ovary have been reported.


Further reading

Eccrine Porocarcinoma Presenting with Unusual Clinical Manifestations: A Case Report and Review of the Literature

Metastatic eccrine porocarcinoma: report of a case and review of the literature

Eccrine porocarcinoma: a report of 2 cases and review of the literature.

Eccrine porocarcinoma: clinical and pathological report of eight cases.

Pigmented porocarcinoma: a case report with review of the literature.

A case of eccrine porocarcinoma: usefulness of immunostain for s-100 protein in the diagnoses of recurrent and metastatic dedifferentiated lesions.

Eccrine porocarcinoma of the scalp.

Porocarcinoma on the face: a rare location. Review of the literature to explore its biological behavior.

Eccrine porocarcinoma. A review of 24 cases.

Carcinoma of Sweat glands.  Pathol Annual. 1987: 22 (part1): 83-124.

Sweat gland carcinoma: A comprehensive review.  Semin Diagn Pathol. 1987 Feb; 4(1) : 38-74





Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)






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