Pilar Cyst

A painless swelling on the dorsum of the scalp had been present for many years in a 36-year-old man. An increase in the size of the lesion prompted the man to seek medical evaluation. Les Trope, MD, Hillel Trope, MD, and Shlomo Trope, MD, of New York included a lipoma and a kerion (a condition associated with tinea infections) in the differential diagnosis. The well-demarcated edge of the lesion and a transillumination test that showed fluid within the lesion ruled out a lipoma. The absence of dryness and scaliness excluded a kerion; moreover, kerions are flat. The punctum on this lesion contributed to its identification as a sebaceous cyst. Also called pilar cyst, or wen, a sebaceous cyst is a benign, slow-growing mass that contains keratinous and/or follicular materials. This nontender cyst typically forms on the scalp but may occur on the ears, face, back, or scrotum. Treatment is surgical for a sebaceous cyst of this size.