Polymorphous sweat gland carcinoma

We describe nine cases of a distinctive cutaneous neoplasm showing features of eccrine adnexal differentiation that were characterized by their variegated histological appearance and low-grade malignant behaviour. The term polymorphous sweat gland carcinoma is proposed to designate these lesions. The tumours presented as large, long-standing, slow growing, dermal nodules showing a marked predilection for the extremities. Six patients were women. The patients were aged 42-70 years (mean, 59.8 years). Histologically, the lesions were characterized by a highly cellular proliferation displaying a variety of growth patterns, including solid, trabecular, tubular, pseudopapillary and cylindromatous, with prominent stromal changes including haemorrhage, hyalinization and cystic change, and displaying moderate cytological atypia and mitoses. Focal areas showing features associated with eccrine differentiation (i.e. tubular structures, small glandular lumina) could be identified in all cases. Clinical follow-up in six cases showed that two of the lesions recurred locally over a period of 3-6 years, and one tumour metastasized to regional lymph nodes 3 years after excision. Polymorphous sweat gland carcinoma should be considered in the differential diagnosis of neoplastic epithelial dermal proliferations; complete but conservative surgical excision appears to be the treatment of choice for these lesions.