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.