Porocarcinoma Arising in a Precursor Poroma

There is a background lesion compatible with an eccrine poroma. However, there is supervening high grade epithelial cell atypia and as well the lesion exhibits an irregular growth pattern within the corium. In regards to the latter individual cells and small nests of severely atypical cells assuming an infiltrative growth pattern amidst a hypervascular stroma. The lesion is best treated and categorized as an excellent prognosis well differentiated porocarcinoma.

Eccrine porocarcinoma is a rare malignant sweat gland tumor that tends to arise on the lower limbs, trunk or head and neck region, can range in size from <1 cm to 10 and assume a nodular or infiltrative growth pattern. clinically, these tumors may be mistaken for seborrheic keratosis, basal cell carcinoma, squamous pyogenic granuloma even an amelanotic melanoma. while uncommon, regional lymph node metastases as well distant have been reported in 20% 10% of cases, respectively. < />>

Reference:
Murilo de Almeida Luz et al. Eccrine Porocarcinoma (Malignant Eccrine Poroma): A Series of Eight Challenging Cases. Clinics (Sao Paulo). 2010 Jul; 65(7): 739-742.

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Slide 1: 42 year-old woman with a leg lesion

Slide 2: This shave excision specimen shows an atypical epithelial proliferation contiguous with the epidermis. The lesion exhibits an interanastomosing growth pattern.

Slide 3: The lesion exhibits an interanastomosing growth pattern with eccrine ductular differentiation.

Slide 4: There is a background lesion compatible with an eccrine poroma.

Slide 5: Focally the proliferation assumes an irregular pattern of growth within the dermis.

Slide 6: Individual cells and small clusters of severely atypical cells are noted amidst an edematous hypervascular stroma. Immunohistochemical stains showed focal staining of the tumor cells for cytokeratin-7 and epithelial membrane antigen. These additional immunohistochemical stains certainly corroborate the diagnosis of a poromatous neoplasm. Based on the infiltrative growth pattern and epithelial cell atypia I do feel that the lesion is best treated and categorized as a well differentiated porocarcinoma.