A Case Report on Alpha-Fetoprotein-Positive Colorectal Cancer.

Alpha-fetoprotein (AFP) is commonly produced by hepatocellular carcinoma and yolk sac tumors, while AFP in colorectal cancer (CRC) is a rare association. We report a case of a patient with primary AFP-producing CRC, which was successfully treated with surgery and adjuvant chemotherapy. This case highlighted the importance of recognizing a case of AFP-producing CRC.  This case report discussed a 59-year-old male who had a history of hepatitis B infection, with two months of intermittent fresh per rectal bleeding. Given his previous burden of hepatitis B infection, and the serum AFP level on admission was high (212.6 ng/mL), this raised suspicions of possible hepatocellular carcinoma. Therefore, a triphasic computed tomography of the liver was performed, which revealed an incidental hepatic flexure lesion with no involvement of the liver. Subsequent colonoscopy revealed a large friable tumor obstructing the whole lumen of the proximal transverse colon. He then underwent an emergency extended right hemicolectomy. Histopathological examination showed a Duke C mucinous adenocarcinoma (T3N2b), with a satisfactory resected margin. Immunohistochemical analysis indicated that the tumor exhibited positivity for MLH1/MSH2/MSH6/PMS2 (+++) and human epidermal growth factor receptor 2 (HER2), and notably, it also stained positive for AFP. The postoperative period was uneventful, and serum AFP level eventually normalized. The patient completed eight cycles (four months) of adjuvant chemotherapy with capecitabine and oxaliplatin (CAPOX) regimen. A follow-up CT scan and colonoscopy showed no evidence of local or distant recurrence after 12 months of surveillance. AFP may be useful for not only hepatocellular carcinoma but also CRC. In particular, this case report has fully demonstrated the unexpected incidence and emphasized the importance of early recognition and appropriate treatment to prevent potential oversights in the diagnosis of CRC.