Eccrine porocarcinoma: a case report with light microscopy and ultrastructure.

A case of eccrine porocarcinoma in a 63-yr-old man is reported. There was a 10 yr history of an abdominal skin lesion which recurred after cautery and metastasized to skin and abdominal lymph nodes. Histologically, the primary tumour was composed of small squamoid cells with ductal lumina. There was intraepidermal nesting spread and an invasive dermal component. Formation of intracytoplasmic lumina in cells with squamoid features, best seen on electron microscopy, pointed towards poral differentiation and was a useful diagnostic feature which persisted in the less well differentiated metastases. The role of hidroacanthoma simplex as a possible preinvasive precursor lesion is discussed. The differential diagnosis from other skin tumours is described. The literature is reviewed. Despite their sometimes innocuous histological appearance, eccrine porocarcinomas are aggressive lesions which require wide local excision of the primary site and consideration of regional lymph node dissection.