Pilomatricoma, also known as calcifying epithelioma of Malherbe or pilomatrixoma, is a small benign adnexal tumor with differentiation toward the matrix portion of hair follicles. A molecular defect in beta-catenin is present in the lesions. Pilomatricoma tends to arise during early childhood as solitary, asymptomatic tumors. Clinically, they present as a small hard, mobile nodule with slight erythema. The head and neck region is most often affected, but other common sites include the trunk and upper extremities. There is a bimodal distribution, with a peak between ages 5 to 15 years and another between ages 50 to 60 years. Although usually sporadic in incidence, familial cases of pilomatricomas have been reported.

Additionally, multiple pilomatricomas have been observed in patients with myotonic dystrophy, familial adenomatous polyposis-related syndromes (including Gardner syndrome), Rubinstein-Taybi syndrome, constitutional mismatch repair deficiency, Kabuki syndrome, trisomy 9, Turner syndrome, and in patients with PENS (papular epidermal nevus with "skyline" basal cell layer). Patients with 6 or more pilomatricomas are more likely to have an underlying syndrome and should, therefore, undergo genetic screening.

Malignant transformation has been reported in fewer than 20 cases. Calcification, ossification, and epidermal perforation may occur.