Primary CD56+ NK/T-cell lymphoma of the rectum accompanied with refractory ulcerative colitis

A case of primary NK/T-cell lymphoma of the rectum accompanied with ulcerative colitis (UC) in a 73-year-old man is reported. He had a 6-year history of repeated admission to our hospital for UC. Total colonoscopy performed 4 months after resolution of refractory UC complicated by cytomegalovirus colitis showed a markedly submucosal tumor in the rectum, which was histologically diagnosed as malignant lymphoma. The findings of computed tomography of the chest and abdomen, gallium scintigraphy, abdominal ultrasonography, and upper gastrointestinal endoscopy showed no abnormal lesions. Therefore, based on a diagnosis of localized rectal lymphoma with UC, proctocolectomy was performed. The resected specimen showed three submucosal tumors in the rectum with local nodal involvement. Histologically, the tumors were characterized by diffusely infiltrating sheets of large atypical lymphoid cells, which were negative for CD4, CD8, and CD20 but were positive for CD56, CD3, and granzyme B. The presence of Epstein-Barr virus (EBV) infection in neoplastic cells was shown by in situ hybridization for EBV-encoded early small RNA1 (EBER-1). Based on these findings, the patient was diagnosed with primary CD56+ NK/T-cell lymphoma of the rectum (stage II(E)). This is the first case report of primary rectal NK/T-cell lymphoma accompanied with UC.