An 18-year-old Japanese woman with no medical history visited a nearby hospital for vomiting. She was diagnosed with superior mesenteric artery syndrome and had a nasojejunal tube placed. Although she was started on tube feeding, the vomiting recurred, and jejunal obstruction was suspected on a small bowel series. She was transferred to our hospital for treatment. We performed a computed tomography examination that revealed a mass lesion in the jejunum. Single-balloon enteroscopy was performed that showed a neoplastic lesion with ulcer, which was diagnosed as diffuse large B-cell lymphoma (DLBCL) based on biopsies. The lesion was considered primary, and a partial resection of the small intestine was performed. Histopathological examination confirmed the diagnosis of DLBCL and no metastases in the resected lymph nodes. The possibility of a tumor should be considered even at a young age, and aggressive examination will be helpful for early detection.
