Cutaneous adnexal carcinoma arising within a solitary cylindroma spiradenoma

Malignant transformation within an adnexal neoplasm with features of spiradenoma and cylindroma is reported in a 60-year-old woman. The malignant component of the tumor consisted of areas of solid carcinoma, with focal squamous metaplasia. In the benign component, apart from the features of spiradenoma and cylindroma, sebaceous differentiation was present adjacent to a cystic space lined by apocrine epithelium. The morphologic composition of this unusual neoplasm supports the concept of a histogenetic relationship between cylindromas and spiradenomas, including their differentiation toward the pilosebaceous-apocrine unit.