Case report: Penile collision tumor comprising HPV-associated squamous cell carcinoma and malignant melanoma

Collision tumors with squamous cell carcinoma (SCC) and malignant melanoma components are extremely rare. We report a case of a penile collision tumor with a component of HPV-associated SCC and malignant melanoma in a 61 year-old man. The patient underwent a partial penectomy and bilateral inguinal sentinel lymph node surgery. Microscopy showed a biphasic tumor with a component of SCC with warty-basaloid morphology, positive for HPV16 and 43, and a malignant melanoma associated with a BRAF mutation. This case posed diagnostic and therapeutic challenges due to the absence of a precise TNM classification and documented treatment guidelines for this tumor type.