Spiradenocylindrocarcinoma: a malignant hybrid tumor.

Background: Eccrine spiradenomas and cylindromas are benign, slowly growing, cutaneous adnexal neoplasms, recently hypothesized to arise from a common pluripotential cell; malignant variants are rare. We found 48 cases of malignant spiradenomas and 33 cases of malignant cylindromas reported in the English literature. Benign tumors demonstrating both spiradenomatous and cylindromatous features have been infrequently reported.