Dowling-Degos disease associated with squamous cell carcinomas on the dappled pigmentation

We report the first case of Dowling-Degos disease associated with squamous cell carcinomas (SCCs) in the pigmented area of Dowling-Degos disease. A 64-year-old Japanese man manifested dappled pigmentation unusually localized to the buttocks, and two pigmented adenoid SCCs had developed on his left pigmented buttock. The other findings of Dowling-Degos disease were comedone-like lesions on the face and back, a finger-like fibroma in the right popliteal fossa, dystrophic fingernails, and a large number of seborrhoeic keratosis-like lesions predominantly on the flexural areas. Another unique clinical feature was the lack of vellus hair on the whole body surface. In addition to thin branching and elongation of rete ridges with basal hyperpigmentation, immature hair follicles surrounded by fibrosis and a lace-like pattern of the hair follicle epithelia were observed histologically. These epithelial hamartomatous features were consistent with Dowling-Degos disease. We speculate that the SCCs developed in relation to an underlying naevoid anomaly in pilosebaceous epithelia of Dowling-Degos disease.