Primary intestinal NK/T cell lymphoma: a clinicopathologic study of 25 Chinese cases.

BACKGROUND Primary intestinal NK/T cell lymphoma is extremely rare and early diagnosis is frequently difficult. The aim of this study is to investigate the clinicopathological findings, immunophenotype, and T cell receptor (TCR) γ gene rearrangement of primary intestinal NK/T cell lymphomas in 25 Chinese cases. METHODS Clinical data of the 25 cases were analyzed. Immunohistochemistry for immunophenotype, in situ hybridization for EBER, and polymerase chain reaction for TCR γ gene rearrangement were investigated. Survival curves according to clinical characteristics were analyzed. RESULTS The median age was 33 years and the median survival was 7 months. The common symptoms consisted of abdominal pain, fever, marasmus, diarrhea, and hematochezia. Endoscopically, the tumors were mainly featured by focal, multifocal or diffuse irregular ulcers, which most frequently emerged in the ascending colon. Histologically, the tumors were characterized by the proliferation of pleomorphic atypical lymphoid cells (ALCs), necrosis, lympho-epithelial lesions, and mixed inflammatory infiltration. The positive frequency of CD3ε was 88.2%, of CD56 was 84%, granzyme B was 90%, and EBER was 84.2%. A total of 12 out of 14 cases (85.7%) highly expressed Ki67. The negative prognostic factors for survival were Ann Arbor stage IIIE or IVE (P = 0.039) and more than one extranodal site of disease (P = 0.019). CONCLUSION Primary intestinal NK/T cell lymphomas most frequently favor young people and have a poor prognosis. Due to the nonspecific clinical and endoscopic findings, it is difficult to distinguish intestinal NK/T cell lymphomas from inflammatory and infectious disorders. Histopathology, immunophenotype, and DNA study play key roles in differential diagnosis.