This study highlights the potential for HSIL to extend into the rectum either as a contiguous patch or isolated islands and the need for heightened surveillance in patients with extensive anal canal HSIL treated with immunodulator therapy. HSIL identified at the limit of the anoscope should be investigated further with colonoscopy, and argon plasma coagulation (APC) ablation can serve as an effective treatment option. Patients are at risk for stricture, but it is unclear what role the UC or the ablation played in stricture formation.