Pigmented epidermal cyst.

A 58-year-old Japanese woman with a pigmented epidermal cyst on the upper arch of the right external ear is described. The blue appearance of the cyst was striking and uncommon in Japanese. Histologically, abundant melanin pigment was observed in the keratinous mass of the cavity, and epithelial cells showed epidermoid keratinization. Increased numbers of melanocytes in the basal layer, large globular cells of melanocytic origin in the spinous layer, and hair-germ-like aggregates of basaloid cells and melanocytes were also observed. The blue clinical appearance is probably due to the rich melanin granules in the cyst, keratinous mass, keratinocytes, and hair-germ-like structures.