Diffuse Involvement of Primary Colorectal Lymphoma Simulating Ulcerative Colitis

Diffuse involvement of colorectal lymphoma masquerading as colitis is a very rare presentation of primary colorectal lymphoma. Detecting occult lymphoma is difficult in the setting of diffuse colonic involvement with no definite mass and inflammatory mucosal changes. We encountered a case of diffuse-type primary colorectal lymphoma simulating ulcerative colitis in a previously healthy 31-year-old woman. Despite multiple mucosal biopsies, the biopsy diagnosis was not made due to unawareness of atypical lymphocytes admixed with dense lymphoplasmacytic infiltration. The present case emphasizes the importance of being aware of this rare presentation of primary colorectal lymphoma in order to avoid misdiagnosis.