Malignant eccrine spiradenoma: a new case report.

Malignant eccrine spiradenoma is an extremely rare skin tumor of sweat gland origin. In most cases, it arises in pre-existing benign eccrine spiradenoma. We report an additional case of malignant eccrine spiradenoma. The present case is of a 75-year-old man with malignant eccrine spiradenoma developed in the right shoulder. He had a 6-year history of a recurrent mass that was removed 2 years ago. The patient then underwent a complete excision. The gross pathologic specimen showed a large cutaneous and subcutaneous multinodular tumor, measuring 6 cm in maximal dimension. Microscopically, there were two distinct morphological components: a benign eccrine spiradenoma and a malignant eccrine spiradenoma of low grade with extensive necrosis. Different histologic patterns were observed such as cylindromatous features. Morphological differentiation in malignant eccrine spiradenoma is variable, sometimes with almost complete loss of eccrine differentiation. Extensive sampling to look for a probable previously benign component is necessary. In the other hand, malignant changes can be easily missed without adequate sampling.