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A 54-year-old woman visits the dermatology clinic requesting removal of a bothersome growth on her left arm. The lesion has been present for over a year and has been slowly increasing in size. She reports that the site is occasionally painful; the pain is often sporadic and “throbbing.” She denies a history of similar lesions or prior history of cancer. Examination reveals a firm, flesh-colored nodule. Palpation elicits tenderness. No similar lesions are noted elsewhere on the patient’s body.
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Cutaneous leiomyomas are uncommonly encountered benign smooth muscle neoplasms of the skin. Approximately 95% of leiomyoma cases occur in the uterus. Cutaneous leiomyoma is the second most common location, accounting for 75% of extra-uterine lesions.1
Cutaneous leiomyomas are divided into 3 main types based on the origin of the smooth muscle: angioleiomyomas, genital, and pilar.2 Angioleiomyomas, also called vascular leiomyoma, originate from smooth muscle within superficial blood vessels. Genital leiomyomas originate within vulvar or areolar smooth muscle. Pilar leiomyomas are derived from the arrector pili musculature.2
Pilar leiomyomas present as firm nodules that range in hue from reddish brown to flesh colored. Pain may be induced by cold or trauma. In most cases, multiple piloleiomyomas are generally found in patients aged 10 to 30 years, whereas solitary piloleiomyomas usually appear later in life. These lesions are located on the trunk or extensor surface of the extremities.3 Skin and genital lesions have similar pathology with tumor cells found within unencapsulated interlacing bundles of smooth muscle fibers admixed with collagen.1
Pilar leiomyomas can be part of an autosomal dominant genetic syndrome. Therefore, when multiple leiomyomas are present, patients should be screened for autosomal dominant genodermatosis. Hereditary leiomyomas are associated with aggressive renal cell carcinoma.4
Stephen Schleicher, MD, is director of the DermDox Center for Dermatology in Pennsylvania, as well as an associate professor of medicine at Commonwealth Medical College and a clinical instructor of dermatology at Arcadia University and Kings College.
References
1. Malhotra P, Walia H, Singh A, Ramesh V. Leiomyoma cutis: a clinicopathological series of 37 cases. Indian J Dermatol. 2010;55(4):337-341. doi:10.4103/0019-5154.74535
2. Hoyt BS, Tschen JA, Cohen PR. Solitary pilar leiomyoma of the nasal dorsum: case report and literature review. Indian J Dermatol. 2015;60(1):82-84. doi:10.4103/0019-5154.147806
3. Boyuk E, Saracoğlu ZN, Arık D. Cutaneous leiomyoma mimicking a keloid. Acta Dermatovenerol Croat. 2020;28(2):116.
4. Hayedeh G, Fatemeh M, Ahmadreza R, Masoud A, Ahmad S. Hereditary leiomyomatosis and renal cell carcinoma syndrome: a case report. Dermatol Online J. 2008;14(1):16.
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