MSFinals-6287

A 70-year-old man presents with perianal pain, bleeding and a palpable mass that is not consistent with a haemorrhoid. He reports having multiple male sexual partners and engaging in unprotected anal sex. An anoscopic examination with biopsy is performed, and the histology confirms a squamous cell carcinoma. The cancer is staged at T3 based on its size. What is the most significant risk factor for this patient’s diagnosis?