Cutaneous leiomyomas (CLs) are benign tumors derived from smooth muscle. There are 3 subcategories based upon the proposed smooth muscle of origin:

• Angioleiomyoma – This most common type of CL originates from the smooth muscle of vessel walls.
• Piloleiomyoma – The next most common type of CL evolves from the arrector pili muscle associated with hair follicles.
• Genital leiomyoma – The least common type of CL is derived from smooth muscle associated with the external genitalia and nipple-areolar complex.

CLs tend to be tumors of adulthood, usually developing after the second decade. There is no reported predominance by race or sex.

Genital CLs are very rare and tend to be solitary; they are more likely nonpainful compared to the other forms of CL. They evolve from dartoic, vulvar, or mammary smooth muscle and may be pedunculated.

Piloleiomyomas are the subtype most commonly associated with the syndrome of hereditary leiomyomatosis and renal cell cancer (HLRCC, also known as Reed syndrome). These patients have germline heterozygous mutation of the fumarate hydratase gene that is inherited in an autosomal dominant fashion. In this condition, CLs develop by the patients' 20s, uterine leiomyomas develop (in women) by their 30s, and type 2 papillary renal cell cancer develops in the patients' 40s.