Seborrheic keratosis with compound nevus, junctional nevus and basal cell carcinoma in the same lesion.

Seborrheic keratosis can be associated with different neoplasms such as basal cell carcinomas, squamous cell carcinomas and melanomas. We describe an unusual case of a man who presented with a brown plaque on his back. The clinical diagnosis was melanoma. Histopathologic examination of the lesion revealed four neoplasms: a compound nevus, a junctional nevus, a superficial basal cell carcinoma and a seborrheic keratosis. Although this association most likely represents a chance phenomenon, we discuss the possibility that the seborrheic keratosis developed from the nevus, and that subsequently the junctional nevus and the basal cell carcinoma developed from the seborrheic keratosis.