[Localization of primary small cell carcinoma with liver metastasis: a rare combination of colonic adenocarcinoma and undifferentiated small cell carcinoma].

Neuroendocrine or small cell cancer (SCC) is a rare tumor, accounting for less than 1% of all colorectal cancers. There is a high rate of metastasis in SCC. Overlying adenomas are commonly present in colorectal SCC. We present a case of a 67-year-old female patient with liver metastasis of SCC. Initially, the primary tumor was not found and the patient underwent chemotherapy. Ten months later, an adenocarcinoma of the right hemicolon was endoscopically diagnosed due to anal hemorrhage and right hemicolectomy was performed. Microscopic examination revealed that the adenocarcinoma was combined with an undifferentiated carcinomatous component. Immunocytochemistry was positive for synaptophysin and chromogranin. In our case a very rare combination of colonic adenocarcinoma and SCC within an overlying adenoma was found.