Small-cell carcinoma of the rectum.

Small-cell carcinoma of the rectum is a rare tumor. We treated a patient with small-cell carcinoma of the rectum with radiation and multidrug regimen being used for small-cell carcinoma of the lung. Within two months of chemotherapy, the primary lesion, as evaluated by rectoscopy, biopsy, and CT scan, had resolved completely. The patient was in complete remission for 12 months after initiation of chemotherapy and died of widespread metastases. At autopsy, no residual tumor was found in the rectum. This case stresses the importance of ultrastructural study in the differential diagnosis of small-cell cancer of the rectum and the fact that this tumor can be treated in the same fashion as for small-cell carcinoma of the lung with multidrug chemotherapy and radiation therapy to achieve local control.