Calcifying Epithelioma of Malherbe

Pilomatrixoma, or calcifying epithelioma of Malherbe, is a benign tumor of the hair follicle matrix. In 1880, Malherbe and Chenantais initially described the lesion as an "epithelioma," believing its origin to be sebaceous. In 1961, Forbis and Helwing introduced the term "pilomatrixoma" after further studies identified the hair follicle matrix as the tumor's true site of origin. Some authors now suggest a panfollicular differentiation. The tumor cells can differentiate into components of the hair matrix, hair cortex, follicular infundibulum, outer root sheath, and hair bulge. Pilomatrixoma most commonly occurs in pediatric patients on the hair-bearing areas of the head and neck but can also affect the extremities and trunk. The preauricular region is the most frequently involved site on the head. Case studies have reported occurrences in other areas, including the periocular region, eyelid, scrotum, and vulva.