Fournier's gangrene with anal cancer: a case report and literature review.

Fournier's gangrene (FG) is a rapidly progressing necrotizing fasciitis affecting the perineum and perianal area, often necessitating urgent surgical intervention. While commonly associated with diabetes, immunosuppression, and infections, malignancy-related FG is uncommon. A 59-year-old female presented with severe left buttock pain and perianal erythema. Imaging studies revealed perineal abscess formation and severe emphysema, leading to a diagnosis of FG. Despite initial surgical debridement and intensive care, persistent perianal induration prompted a biopsy, which confirmed squamous cell carcinoma with HPV 16 positivity. Chemoradiotherapy was administered, achieving significant regression of the tumor and lymph nodes. Robotic abdominoperineal resection was subsequently performed, achieving complete tumor regression (ypT0N0). The patient recovered well initially, but systemic recurrence occurred 10 months after surgery. This case illustrates the infrequent coexistence of FG and anal cancer, highlighting the necessity for early malignancy evaluation in patients with FG.