Basal cell carcinoma occurring around the anus: A case report

Perianal basal cell carcinoma (BCC) is an exceedingly rare malignant tumor, distinct from ultraviolet-associated BCC that arises in sun-exposed regions. Its nonspecific clinical manifestations—often resembling melanoma, dermatitis, eczema, or anal fistula—frequently lead to diagnostic challenges. This study presents a case of perianal BCC with a disease course exceeding one year. During this period, the patient underwent hospitalization for radical sigmoidectomy to address concurrent sigmoid colon cancer, yet the BCC remained undetected. Subsequent outpatient magnetic resonance imaging (MRI) initially suggested anal fistula. Definitive diagnosis was ultimately achieved through histopathological examination. The patient underwent wide local excision with clear margins (R0 resection), followed by an uneventful postoperative recovery. At present, the surgical site has healed satisfactorily, with no evidence of recurrence observed during follow-up.