Giant melanosomes in the dysplastic nevus syndrome. Electron microscopic observations.

Multiple pigmented lesions including benign lentigines, typical nevi, and dysplastic nevi from 3 patients with the dysplastic nevus syndrome contained giant melanosomes (GM). Ultrastructurally the GM were composed of microvesicles, but lacked limiting membrane and filamentous internal structure. As such, they resembled the GM found in 4 other patients with dysplastic nevus syndrome, leopard syndrome and ocular albinism, but differed from those found in the café-au-lait spots of neurofibromatosis, nevus spilus, vitiliginous achromia, and certain animals.