Rare recurrence pattern after complete response to chemotherapy in a patient with rectal cancer: a case report

Colorectal cancer (CRC) often metastasizes to the liver, lungs, lymph nodes, and peritoneum but rarely to the bladder, small intestine, and skin. We here report the rare metastasis of anal cancer in the left bladder wall, followed by metastases to the small intestine and skin, after abdominoperineal resection and left lateral lymph node dissection with chemotherapy in a patient with clinician Stage IVa disease.

A 66-year-old man presented with 1-month history of bloody stool and anal pain and diagnosed with clinical Stage IVa anal cancer with lymph node and liver metastases (cT3, N3 [#263L], M1a [H1]). Systemic chemotherapy led to clinical complete response (CR) for the liver metastasis and clinical near-CR for the primary tumor. Robot-assisted laparoscopic perineal rectal resection and left-sided lymph node dissection were performed. Computed tomography during 18-month postoperative follow-up identified a mass in the left bladder wall, which was biopsied with transurethral resection, was confirmed as recurrent anal cancer by histopathologic evaluation. After two cycles of systemic chemotherapy, partial resection of the small intestine was performed due to bowel obstruction not responding to conservative therapy. The histopathologic evaluation revealed lymphogenous invasion of the muscularis mucosa and subserosa of all sections. Ten months after the first surgery for bowel obstruction and two months before another surgery for obstruction of the small intestine, skin nodules extending from the lower abdomen to the thighs were observed. The histopathologic evaluation of the skin biopsy specimen collected at the time of surgery for small bowel obstructions led to the diagnosis of skin metastasis of anal cancer. Although panitumumab was administered after surgery, the patient died seven months after the diagnosis of skin metastasis.

This case illustrates the rare presentation of clinical Stage IVa anal cancer metastasizing to the bladder wall, small intestine, and skin several years after CR to chemotherapy.