Extranodal NK/T-cell Lymphoma, Nasal Type

Extranodal NK/T-cell lymphoma, nasal type (ENKTL) is uncommon in the United States. We report 73 patients with ENKTL, including 49 men and 24 women (median age, 46 y). Sixty-three patients had nasal/upper aerodigestive tract disease; 10 had extranasal disease involving skin, small intestine, epiglottis, testis, adrenal glands, kidney, and breast. Complete staging data were available for 68 patients: 44 stage I/II and 24 stage IV. Fifteen of 69 (22%) had lymphadenopathy and 10/63 had bone marrow involvement. Histologically, 67/73 (92%) showed necrosis, and 48/70 (69%) had an angiocentric/angiodestructive growth pattern. The neoplastic cells showed a wide spectrum: medium sized (n=34), mixed small and large (n=21), large (n=13), and small (n=5). In situ hybridization for Epstein-Barr virus-encoded small RNA was positive in every case. Immunohistochemical studies showed expression of cytotoxic markers (100%), T-bet (96%), CD2 (96%), CD3 (93%), CD56 (90%), and ETS-1 (64%). Ki-67 was ≥60% in 46% cases. Therapy was known for 64 patients; 14 received only chemotherapy, 8 radiation alone, and 42 received combined radiation and chemotherapy. Median survival was 4.2 years, and 5-year overall survival was 46% (median follow-up, 3.8 y). Extranasal disease, high International Prognostic Index score, and high proliferation rate correlated with poorer prognosis. We conclude that ENKTL cases in the United States are similar to those reported in Asia and other countries. Absence of the angiocentric/angiodestructive pattern and presence of lymphadenopathy, features underemphasized in the literature, occurred in appreciable subsets of patients. The International Prognostic Index score, anatomic site of disease, and proliferation rate had prognostic value in this patient cohort.