Cutaneous leiomyoma with cytologic atypia, akin to uterine symplastic leiomyoma

Smooth muscle tumors of the skin with cytologic pleomorphism and mitotic activity have traditionally been characterized as leiomyosarcomas, despite having a benign clinical course. In the uterus, there is a smooth muscle tumor known as symplastic leiomyoma, which typically has cytologic pleomorphism without significant mitotic activity.

The objective was to illustrate by case report the unusual histologic variant of the cutaneous pilar leiomyoma analogous to the symplastic leiomyoma of the uterus.

A 54-year-old woman presented with a clinical picture of cutaneous leiomyoma but had histologic features of nuclear hyperchromasia and pleomorphism, but rare mitoses.

Management of this patient included excision of the involved area.

Symplastic leiomyoma is an atypical uterine leiomyoma with cytologic atypia. We present the case of a patient with cutaneous leiomyomas that histologically demonstrated similar features to a uterine symplastic leiomyoma. We believe that this represents a distinct histologic variant of the cutaneous pilar leiomyoma analogous to the symplastic leiomyoma of the uterus.