Malignant eccrine spiradenoma with smooth muscle cell differentiation: histological and immunohistochemical study.

Malignant transformation in a benign eccrine spiradenoma is rare. Since it was first reported in 1972, 31 cases have been reported. Of these, six cases had sarcomatous components, mainly osteosarcomatous, and one had rhabdomyoblastic differentiation. A case is presented in which there were some small nodules of benign eccrine spiradenomas adjacent to a large nodule of malignant eccrine spiradenoma with leiomyosarcomatous components, determined by histologic and immunohistochemical studies.