[A Case of Small Intestinal Malignant Lymphoma Presenting with Perforated Peritonitis].

An 85-year-old man presented to the emergency department with vomiting. He had tenderness in the left abdomen and under the umbilicus. Laboratory data showed an increase in the inflammatory response. Enhanced abdominal computed tomography showed thickening ofthe small intestinal wall in the lower left abdomen with a small amount ofadjacent free air. The fat tissue around the small intestine also revealed a high density area suggestive of inflammation. A diagnosis of peritonitis caused by intestinal perforation was made and an emergency operation was performed. We resected part of the ileum about 90 cm from the ileum end. The resected specimen showed a 1 by 1 cm mass with an ulcer and perforation at the base of the tumor. Histopathological findings revealed densely increased numbers of monomorphic medium-sized lymphoma cells infiltrating into all layers ofthe intestine. Immunohistochemically, the lymphocytes were positive for CD3, CD20, CD30, and CD79a. We diagnosed diffuse large B-cell lymphoma. Two cycles ofchemotherapy were given post-operatively. A recurrence was not observed. After chemotherapy he was transferred to rehabilitation.