Adenocarcinoma of the Rectum with Choriocarcinomatous Differentiation: A case report

ABSTRACT

A choriocarcinoma of the rectum is extremely rare and has a very poor prognosis. Its rarity and the obscurity of its histogenesis make the entity of disease hard to define. We report a case of a choriocarcinoma of the rectum which showed synchronous liver and lung metastasis. A 52-year- old male patient presented with tenesmus, hematochezia and pain on defecation for 4 months. The preoperative colonoscopy revealed a mass at the rectum, 3 cm proximal to the anal verge. The biopsy revealed a poorly differentiated adenocarcinoma. An abdominoperineal resection was performed, and the pathologic examination confirmed a choriocarcinoma arising from an adenocarcinoma. Immunostain for beta-human chorionic gonadotropin (hCG) was strongly positive for the choriocarcinoma component. Serum hCG checked postoperatively was as high as 4,222 IU/L, but the serum carcinoembryonic antigen (CEA) was normal. Although chemotherapy was begun at the 5th week after the operation, the patient died on the 47th day after the operation. A choriocarcinoma of the colon or the rectum is very rare and is aggressive. Although radical resection and chemotherapy are performed, the clinical outcome is very disappointing. Even though a choriocarcinoma of the colon or the rectum is very rare, it should be included on the list for differential diagnosis of a colorectal carcinoma.