Primary Adenocarcinoma with Focal Choriocarcinomatous Differentiation in the Sigmoid Colon.

Primary colorectal choriocarcinoma is a rare neoplasm. Only 19 cases have been reported worldwide, most of which involved adenocarcinomas. The prognosis is usually poor, and the standard therapy for this tumor has not been established. A 61-year-old woman presented with constipation and lower abdominal discomfort. She was diagnosed with primary adenocarcinoma with focal choriocarcinomatous differentiation in the sigmoid colon and liver metastasis. Because the serum beta-human chorionic gonadotropin level was not significantly elevated, and because only focal choriocarcinomatous differentiation was diagnosed, we selected the chemotherapy regimen that is used for the treatment of metastatic colorectal adenocarcinoma. The patient survived for 13 months after the initial diagnosis. This is the first case in Korea to assess the suppressive effects of the standard chemotherapy for colorectal adenocarcinoma against coexisting colorectal choriocarcinoma and adenocarcinoma.