Malignant transformation of eccrine spiradenoma.

Two patients are described in whom malignant transformation occurred within an eccrine spiradenoma. Their findings were compared with those of six similar patients from the literature, and a characteristic clinicopathologic picture was evident. The typical history was one of rapid enlargement of a cutaneous nodule of long standing. The neoplasms were composed, at least in part, of large, markedly atypical basaloid cells with numerous mitotic figures. Adjacent benign spiradenoma was observed microscopically in each case, and some of the carcinomas retained architectural features reminiscent of spiradenoma. One patient died of disseminated tumor, but follow-up was short or lacking in several cases. Malignant transformation of eccrine spiradenoma shares many clinical and pathologic features with malignant transformation of dermal cylindroma.