Rapidly growing giant pilomatricoma in the right parotid region of a pregnant woman.

Pilomatricoma is a benign tumor arising from the primitive basal cells of the epidermis that differentiate into hair matrix cells. Mutations in the CTNNB1 gene, which encodes β-catenin (a protein involved in hair growth), play an etiological role in the development of pilomatricoma. A 34-yearold woman presenting with a mass in the right parotid region underwent an excisional biopsy. The mass was conclusively diagnosed as pilomatricoma. During pregnancy, the mass grew from 1 cm to 5 cm in diameter and was accompanied by pain and tenderness. The growth may have been facilitated by the increased production of estrogen and progesterone, which bind to receptors located in the outer root sheath cells of the hair follicles. No recurrence was observed during 6 months of follow-up.