[Eccrine porocarcinoma. A review of 24 cases]

From 1982 to 1992, 24 cases of eccrine porocarcinomas were recorded in our files. They always present as solitary well circumscribed nodules or plaques of 0.5 to 2 cm and they are mainly located on the face and the lower limbs in patients, predominantly females, aged of more than 5 decades. The average evolution time before diagnosis was 2 years; a case was observed in a 12-y-old patient with xeroderma pigmentosum. After surgical removal, only one local recurrence and one case with lymph node metastases were observed. The lesions showed two different histological types: the former is initially characterized by the intra-epidermal spreading of well circumscribed cell nests and by a secondary invasion of the dermis, the latter exhibits a trabecular pattern penetrating the dermis, sharing some microscopic aspects with the benign eccrine poroma. Whatever the histological type, the tumor is mainly built up by small cuboidal cells together with some large clear cells; the latter exhibit often atypias, which are focally distributed in the trabecular poroma-like variant. Dyskeratosis, malpighian metaplasia and necrotic comedo-like foci are frequently encountered. Ductal differentiation may be intracellular and occur together with focal keratinization. In one case with intra-epidermal cell islets, lymph node metastases showed the same cellular pattern; this superficial spreading type of porocarcinoma has the same malignant behaviour as the trabecular penetrating type. The eccrine porocarcinomas derive from the acrosyringeal cells: the ductal structures and the foci of keratinization express the epithelial membrane antigen (EMA), the carcino-embryonic antigen (CEA) and the alpha-lactalbumine related antigen; the tumor cells are S100 proteine negative.(ABSTRACT TRUNCATED AT 250 WORDS)