ABSTRACT
Collision tumors in which two different skin tumors appear in one lesion have often been reported. The cause of the collision tumor is not clearly known, but there is an opinion that it is a simple coincidence, and other authors assumed that one tumor will cause another. This rare but well-documented phenomenon often presents a diagnostic challenge to dermatologists due to its unusual and nonspecific presentation. We experienced a case of a 32-year-old woman who came to our hospital with a 1.5×1.5-cm-sized red-brown nodule with a surrounding brown patch on her right posterior shoulder that had been present since her childhood. Histologically, this lesion was thought to be a collision tumor with dermatofibroma and Ito nevus in the same lesion. No further treatment was done for this patient and a close follow-up is ongoing. Herein, we reported a first case of collision tumor with dermatofibroma and Ito nevus.