[Small Intestinal Metastasis from Lung Cancer with Infiltration into Other Organs-Review of the Literature].

We report a case of metastasis to the small intestine from squamous cell carcinoma of the lung with fistula formation in the adjacent small intestine as well as an analysis of reported cases in Japan of small intestinal metastasis from lung cancer invading other organs. A 63-year-old man was diagnosed with squamous cell carcinoma of the lung as a result of pneumonia. Chemoradiotherapy was administered and sequential chemotherapy was performed, but a single brain metastasis of right parietal lobe was detected 6 months later. Tumor resection was performed. Twelve months after the lung cancer diagnosis, metastasis of the small intestine was detected. Single-incision laparoscopic surgery with partial resection of the small intestine was performed. The tumor had invaded the abdominal wall and 2 parts of the small intestine and had formed a fistula with part of the small intestine. Subsequently, peritoneal dissemination recurred and the patient received the best supportive care. There are 10 reported cases in Japan of small intestinal metastasis from lung cancer invading other organs. Analysis of the reported cases indicates a poor prognosis for patients with fistula. Resection can improve prognosis in patients with primary lung cancer and without distant metastasis. Surgical resection should be considered even if metastasis in the small intestine from lung cancer has invaded other organs.