Pityrosporum ovale/orbiculare in papillomatous nevus cell nevi.

62% of 200 papillomatous nevus cell nevi compared to 45% of 40 seborrheic keratoses showed the presence of Pityrosporum ovale/orbiculare (Malassezia furfur) on their surface, supposedly representing a saprophytic state of the microorganisms in vivo. The papillomatous nevus cell nevi were of the compound or dermal type. Significant inflammation, dysplasia or major changes in color were absent. Electron microscopy revealed the characteristic, sometimes budding fungal cells. A relationship between the presence of Pityrosporum organisms and papillomatosis is discussed.