Collision Tumor between Trichofolliculoma and Melanocytic Nevus.

Trichofolliculoma (TF) is a hamartomatous hair follicle-related tumor, clinically described as a dome-shaped papule with a central pore crossed by one or more silky white hairs. Histologically, it described as a cystic cavity containing keratinous debris, hair shaft fragments, and numerous hair follicles arising from its linings. Collision or compound tumors are a coexistence of two or more identifiable tumors in the same lesion. We present a case of a 47-year-old man with a lesion on his left cheek clinically characterized as a TF. However, the histopathological study reveals a collision tumor involving a TF and a melanocytic nevus. Collision tumors involving melanocytic nevi and hair follicle-related tumors have been previously reported, such as desmoplastic trichoepithelioma, epidermoid cyst, folliculosebaceous cystic hamartoma, and trichoadenoma.