Primary small‐cell carcinoma in the lung was found after the cold snare polypectomy of the small metastatic lesion in the cecum: A case report

Metastasis from small‐cell lung cancer to the colon is very rare. A 74‐year‐old man without respiratory or abdominal symptoms underwent a follow‐up lower gastrointestinal endoscopy after a polypectomy. He was diagnosed with a 5 mm IIa non‐hyperplastic polyp in the cecum and underwent a cold snare polypectomy. The histopathological findings confirmed the diagnosis of small cell carcinoma. The tumor was positive in the deep margins of the submucosal layer. Subsequent systemic examination revealed a mass in the lower lobe of the left lung. Thus, the tumor in the cecum was determined to be a colorectal metastasis from primary small‐cell carcinoma of the lung. Metastasis to the colon was diagnosed as small‐cell lung cancer based on local positivity for thyroid transcription factor‐1 and morphologic and immunochemical features. To our best knowledge, this is the first report of colon metastasis from small cell carcinoma identified by endoscopic treatment.