Primary colorectal lymphoma comprising both components of diffuse large B-cell lymphoma and mucosa-associated lymphoid tissue lymphoma combined with cytomegalovirus colitis.

A 16-year-old girl presented to our hospital with diarrhea and abdominal pain. The macroscopic findings of colonoscopy revealed multiple submucosal tumors and multiple ulcers, which were localized in the sigmoid colon, and diffuse granular mucosa which extended to the total colon. The pathological diagnosis was malignant lymphoma comprising both components of diffuse large B-cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue (MALT) lymphoma, because the large lymphoma cells were CD20+, CD10-, and CD5-. Furthermore, immunohistochemical analysis of colorectal biopsy samples from multiple ulcers revealed cytomegalovirus (CMV)-positive cells. The patient was diagnosed with primary colorectal lymphoma comprising both components of DLBCL and MALT lymphoma combined with CMV colitis. She received anti-viral medication and chemotherapy.