Primary Diffuse Large B-Cell Lymphoma of the Rectosigmoid Colon in a Patient With Ulcerative Colitis Who Never Received Immunosuppression

Primary rectal lymphoma is extremely rare, accounting for approximately 0.05% of all primary rectal neoplasms. We present a patient with long-standing ulcerative colitis, who was never treated with immunomodulators or biologic agents, diagnosed with primary diffuse large B-cell lymphoma of the rectosigmoid colon, and achieved remission after chemotherapy. As per current data, incidence of primary colorectal lymphoma has been associated with medications used for inflammatory bowel disease treatment, such as thiopurine, methotrexate, or tumor necrosis factor-α antagonist, and not with the inflammation itself. Given the rarity of this phenomenon, more data should be gathered before determining that no such association exists.