Hereditary Leiomyomatosis and Renal Cell Cancer: A Case Report of Pilar Leiomyomatosis with History of Kidney Cancer and Review of the Literature.

Pilar leiomyoma or piloleiomyoma is a benign neoplasm of the smooth muscle arising from the arrector pili muscle. It manifests as brown to red firm papulonodules with sites of predilection being the face, trunk, and extensor surfaces of the extremities. Histologically, the lesions exhibit ill-defined dermal tumors with interlacing fascicles of spindle cells. Some genodermatoses are characterized by the development of visceral tumors and cutaneous leiomyomatosis such as Reed's syndrome, and hereditary leiomyomatosis and renal cell cancer (HLRCC). A 55-year-old male presented with reddish-brown papules and nodules on the face and upper back, accompanied by sharp episodic pain on the face. He had undergone nephrectomy for renal cancer 9 years ago, and his younger brother had similar cutaneous manifestation. Histopathologic findings were consistent with pilar leiomyoma, showing bundles of smooth muscle tumors in the dermis. Based on the clinical information including clinical features, past medical history, and family history, HLRCC was highly suspected. To confirm the diagnosis, whole exome sequencing was performed using peripheral blood, which revealed a novel point mutation (c.739G>A, p.Glu247Lys) in the fumarate hydratase () gene. We describe a confirmed case of HLRCC, which is a genetic disorder with a potential to cause visceral cancers, which dermatologists might overlook as a benign condition.