Clinicopathological and Immunohistochemical Study of Eccrine Porocarcinoma (Malignant Eccrine Poroma)

Abstract

Porocarcinomas are thought to be differentiated into the acrosyringeal portion of the sweat duct, and they are relatively rare. It may develop from a long standing eccrine poroma undergoing malignant transformation or may arise de novo. We evaluated pathological and immunohistocheimical findings of six cases of eccrine porocarcinoma. Special stains (PAS and PAS with diastase) and immunohistochemical stainings (CEA, CAM5.2, CK7, bcl‐2, p53 protein, and MIB‐1) were performed. We observed asymmetrical architecture, cytological pleomorphism, prominent nucleoli, ductal differentiation, intracytoplasmic lumina, mitotic activity, and melanin colonization. Three patients were male and four patients were female. The average age was 76 years. The time interval from tumor onset to treatment ranged from 6 months to 10 years. The mean size was 3.2 cm, and the mean depth of invasion was 1.0 cm. Four tumors were found on the head, one on the hip, and one on the foot. Regional lymph node metastases were noted in one case. Microscopically, luminal spaces and intracytoplasmic lumina were noted in all cases. Immunohistochemically, the mean MIB‐1 index was 41%. P53 immunoreactivity was detected in five cases. Interestingly, a case of porocarcinoma with lymph node metastases showed high mitotic figures as well as less lymphocytic infiltration.