Case History/Examination
A 73-year-old man underwent sigmoidectomy with lymph node dissection for stage Ⅱ sigmoid colon cancer 4 years ago. Afterward, he was carefully monitored using chest- and abdominal computed tomography (CT), serum tumor markers, and colonoscopies. No evidence of metastasis or anastomotic recurrence was observed until 4 years and 3 months postoperatively when he experienced anal bleeding during defecation, initially felt to be caused by internal hemorrhoids. Anal examination revealed a pink, firm perianal tumor (Figure A). On biopsy, the sample showed heterotypic columnar epithelium arranged in irregular duct-like, amalgamation duct-like, and comb-like configurations under stratified squamous epithelium, indicating that the tumor was a metastasis of the colonic adenocarcinoma (Figure B). The patient was oxygen-dependent due to pulmonary fibrosis and emphysema, and had a history of rheumatoid arthritis and variant angina, which contraindicated rectal amputation.