A 10-year-old boy presents with an asymptomatic firm nodule on his right cheek; it has enlarged slowly in size over the past year. The boy is in good health, without developmental or behavioral abnormality. On squeezing the lesion, a longitudinal crease is noted traversing the center of the growth. No similar lesions are noted elsewhere.
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Pilomatricomas are benign tumors of the skin that arise from hair follicle matrix cells.1 The typical presentation is that of a solitary firm nodule located on the head, neck, or upper extremity; lesions are rarely found on the trunk or lower extremity.1,2 Children and adolescents are the most commonly affected age groups, and there is a female predominance. The tumor is slow-growing and usually asymptomatic.
The majority of pilomatricomas contain mutations of the CTNNB1 gene, which codes for the protein beta-catenin.3 Several disorders are associated with multiple nodules, including myotonic dystrophy, Gardner syndrome, and Turner syndrome.
Diagnosis is based on physical examination and supported by a positive “skin crease sign,” the appearance of a central longitudinal crease when the lesion is squeezed along its margin.4 Histopathology reveals a well-encapsulated tumor containing 2 distinct cell populations, with basaloid cells located toward the periphery and shadow cells occupying the central portion. Surgical excision with adequate margins is curative. Pilomatrix carcinoma is very rare and most commonly occurs in elderly white males.5
Rebecca Geiger, PA-C, is a physician assistant at the DermDox Dermatology Center in Hazleton, Pennsylvania. Stephen Schleicher, MD, is an associate professor of medicine at the Commonwealth Medical College in Scranton, Pennsylvania, and an adjunct assistant professor of dermatology at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia.
- Bae E, Meehan S, Geronemus R, Bae Y . Multiple pilomatricomas in a 41-year-old Asian woman. J Am Acad Dermatol. 2016.74:AB201.
- Rao J. Pilomatrixoma. Medscape. http://emedicine.medscape.com/article/1058965-overview. Updated August 12, 2016. Accessed May 4, 2017.
- Porter M, Fischer A. Multiple heritable pilomatricomas in a mother-daughter pair. J Am Acad Dermatol. 2016:74:AB63.
- Kim IH, Lee SG. The skin crease sign: a diagnostic sign of pilomatricoma. J Am Acad Dermatol. 2012:67:e197-e198.
- Herrmann J, Allan A, Trapp KM, Morgan MB. Pilomatrix carcinoma: 13 new cases and review of the literature with emphasis on predictors of metastasis. J Am Acad Dermatol. 2014:71:38-43.e2.