A case of desmoplastic leiomyosarcoma: a rare variant of cutaneous leiomyosarcoma.

Desmoplastic leiomyosarcoma is a rare histologic variant of cutaneous leiomyosarcoma seen more commonly in men in their 50s and 60s. This neoplasm typically presents as a solitary, enlarging red-pink nodule or plaque on the extensor surfaces of lower extremities. Its unusual histology mimics other cutaneous desmoplastic lesions and the knowledge of this entity and use of an appropriate immunohistochemical panel is essential to arrive at the correct diagnosis. We report a rare case of desmoplastic leiomyosarcoma of the left flank in a 66-year-old male who presented with itching and pain in a long-standing skin lesion. Histopathology showed the presence of individual and small aggregates of spindle to pleomorphic cells with numerous mitoses in a densely fibrotic stroma. Immunohistochemically, the cells were positive for smooth muscle actin, heavy chain myosin, and desmin, confirming their smooth muscle origin. A diagnosis of desmoplastic leiomyosarcoma was made. We discuss the case with a short review of the literature.