A rare case of Epstein-Barr virus-positive diffuse large B-cell lymphoma, not otherwise specified, in a patient with ulcerative colitis.

While colorectal cancer is a likely complication associated with inflammatory bowel diseases such as ulcerative colitis, malignant lymphoma occurs less frequently. We report the case of a patient with ulcerative colitis having Epstein-Barr virus-positive diffuse large B-cell lymphoma, not otherwise specified (EBV + DLBCL, NOS), which was maintained in clinical remission with 5-aminosalicylic acid. The patient had received a diagnosis of total ulcerative colitis 5 years ago. A recent colonoscopy revealed a 35 mm protruding lesion with depression in the sigmoid colon, and histopathological examination confirmed the presence of EBV + DLBCL, NOS. The patient has undergone six courses of chemotherapy without recurrence of lymphoma and will continue to be monitored periodically. Patients with ulcerative colitis must be followed up with periodic colonoscopies and imaging studies regardless of their background, treatment, and symptoms to ensure the prevention of complications. Furthermore, while special attention must be paid to the commonly occurring colorectal cancer on account of its association with the patient's prognosis, the possibility of the incidence of malignant lymphoma must not be ignored.