CEA-producing urothelial cell carcinoma with metastasis presenting as a rectal adenocarcinoma

This is a case study of a 61-year-old male who presented with difficult defecation for 1 month. A circumferential submucosal rectal tumor was noted on a digital rectal examination and colonoscopy. Laboratory examination revealed high serum levels of carcinoembryonic antigen (CEA; 43.75 ng/mL) and carbohydrate antigen 19-9 (CA19-9; 11,790 U/mL). In addition, tumor biopsies revealed a poorly differentiated adenocarcinoma of the rectum with intact mucosa. The patient had history of advanced stage-T2 urothelial cell carcinoma of bladder, which had been downstaged to T0 by neoadjuvant chemotherapy followed by radical cystectomy 1 year prior. After investigating the initial bladder tumor specimens, a small portion of the tumor with high CEA expression comparable to the submucosal rectal tumor was found. The size of the tumor was reduced and the levels of the tumor markers decreased after administering FOLFIRI chemotherapy targeted at the adenocarcinoma. Although neoadjuvant chemotherapy may have a selective pressure to eliminate most urothelial cell carcinoma, physicians should be aware that it can lead to rectal metastasis via CEA-producing components.