NK-cell enteropathy: a benign NK-cell lymphoproliferative disease mimicking intestinal lymphoma: clinicopathologic features and follow-up in a unique case series

Intestinal T-cell and natural killer (NK)-cell lymphomas are clinically aggressive and can be challenging to diagnose in small endoscopic biopsies. We describe 8 patients in whom atypical NK-cell lymphoproliferative lesions mimicked NK-or T-cell lymphoma. The patients (2 men; 6 women; ages 27-68 years) presented with vague gastrointestinal symptoms with lesions involving stomach, duodenum, small intestine, and colon. At endoscopy, the lesions exhibited superficial ulceration, edema, and hemorrhage. Biopsies revealed a mucosal infiltrate of atypical cells with an NK-cell phenotype (CD56(+)/TIA-1(+)/Granzyme B+/cCD3(+)), which displaced but did not invade the glandular epithelium. Epstein-Barr virus-encoded RNA in situ hybridization was negative, and T-cell receptor-gamma gene rearrangement showed no evidence of a clonal process. Based on an original diagnosis of lymphoma, 3 patients received aggressive chemotherapy followed by autologous bone marrow transplantation in 2. Five patients were followed without treatment. However, no patient developed progressive disease or died of lymphoma (median follow-up, 30 months). Repeat endoscopies in 6 of 8 patients showed persistence or recurrence of superficial gastrointestinal lesions. This unique entity mimics intestinal and NK-/T-cell lymphomas on endoscopic biopsies and can result in erroneous diagnosis, leading to aggressive chemotherapy. We propose the term NK-cell enteropathy for this syndrome of as yet unknown etiology. (Blood. 2011; 117(5): 1447-1452)