Osteo-nevus of Nanta: a case report and review of the Japanese literature.

We reported a 58-year-old Japanese male with osteo-nevus of Nanta on his right cheek. Histological examination revealed nests of nevus cells throughout the entire dermis. Just beneath the nevus in the lower dermis, several basophilic oval-shaped membranous structures were positive with Kossa stain. No inflammatory infiltrate or foreign-body granuloma were seen. We reviewed 28 cases of osteo-nevus of Nanta reported in the Japanese literature and discussed the pathogenesis of ossification in the lesions of nevus cell nevi.