A 72-year-old women reports perianal rash, pruritus, and intermittent bleeding for the past 3 years. She has tried topical creams and topical steroids without improvement. On examination, a 1-cm raised erythematous lesion is seen at the anal margin. A biopsy of the lesion demonstrates large cells with pale, clear cytoplasm. Endoscopic examination is unremarkable. What is the recommended treatment for her?