Synchronous small cell carcinoma and adenocarcinoma of the rectum.

Small cell carcinoma (SCC) is derived from neuroendocrine cells primarily found in the lung. Extra-pulmonary SCC is relatively rare, comprising <5% of all SCCs. Most extra-pulmonary SCCs are found in the gastrointestinal tract; however, SCC of the rectum is extremely rare. The tumour biology of rectal SCC is similar to that of pulmonary SCC, an aggressive tumour that results in frequent distant metastases associated with poor response to chemotherapy. Combination chemotherapy, based on regimens for pulmonary SCC, has been used to treat extra-pulmonary SCC, and surgical resection followed by radiation therapy has been suggested; however, an optimal treatment modality has not been established due to the rarity of these cases. Here, we present a case of synchronous SCC and adenocarcinoma of the rectum that was managed by radical surgery followed by chemotherapy, but recurred with rapid progression in the regional and distant lymph nodes.