Follicular lymphoma-related colitis resembling ulcerative colitis.

Among the various manifestations of colonic involvement in malignant lymphomas, an ulcerative colitis-like appearance is rare. Herein, we describe a case in which extranodal colonic involvement resembled ulcerative colitis in a patient with advanced follicular lymphoma. A 59-year-old Japanese man with diarrhea and body weight loss was referred to our hospital. Computed tomography (CT) revealed systemic lymphadenopathy, splenomegaly, and thickening of the sigmoid colon and rectum walls. F-fluorodeoxy-glucose positron emission tomography (F-FDG-PET/CT) revealed intense tubular F-FDG accumulation extending from the rectum to the colon at the hepatic flexure and much weaker accumulation in the systemic lymph nodes, bone marrow, and spleen. The isotope-enriched areas had an ulcerative colitis-like appearance as shown via colonoscopy. The patient was ultimately diagnosed with follicular lymphoma (stage IV A, grade 1) based on a pathological examination of the neck lymph nodes, iliac bone marrow, and colon. After six courses of chemotherapy (R-CHOP), F-FDG-PET/CT confirmed complete remission of the lymphoma including the colonic lesion. This is presumably the first case of ulcerative-like colitis caused by a follicular lymphoma. As a novel approach, the lymphoma-related colitis was detected by comparing the pathology results and the F-FDG-PET/CT results.