[CD5-positive diffuse large B-cell lymphoma with gastrointestinal infiltration presenting with protein-losing enteropathy].

Protein-losing enteropathy is rarely associated with malignant lymphoma. This report describes the case of a 67-year-old man with diffuse large B-cell lymphoma (DLBCL) and concomitant protein-losing enteropathy who was admitted to our hospital for evaluation of watery diarrhea, edema, and abdominal fullness. On admission, the patient reported a history of weight gain. Subsequent examination showed ascites, hepatosplenomegaly, and hypoalbuminemia. Notably, 99mTc-labeled human serum albumin scintigraphy revealed protein loss from the intestine, and the patient was diagnosed with protein-losing enteropathy. Endoscopy revealed erosive and edematous hyperplasia of the gastric-colonic mucosa, and histopathological evaluation of a biopsy specimen showed proliferation of CD20 and CD5 tumor cells. Thus, the diagnosis of DLBCL was histopathologically confirmed. Lymphomatous infiltration of the bone marrow was observed; however, no lymphadenopathy was detected. Based on these findings, the patient was diagnosed with protein-losing enteropathy associated with gastrointestinal infiltration of CD5 DLBCL. Hypoalbuminemia and diarrhea improved following the initiation of R-CHOP regimen. The DLBCL showed a favorable response to treatment, and gastrointestinal lesions and hepatosplenomegaly improved, along with the resolution of protein-losing enteropathy.