OBJECTIVETo study the clinicopathologic features and prognostic factors of extranodal nasal type NK/T-cell lymphoma (EN-NK/TCL) in Chinese patients.

METHODSFifty-five cases of EN-NK/TCL diagnosed in Chinese patients during the period from 1998 to 2007 were studied by light microscopy, immunohistochemistry and in-situ hybridization. The follow-up information was analyzed.

RESULTSThe male-to-female ratio was 1.89:1. The median age of the patients was 38 years. The commonest sites of involvement included nasal cavity and adjoining tissue (85.5%). Histologically, EN-NK/TCL was composed of small to medium-sized lymphoid cells. Angiocentric and angiodestructive growth patterns, coagulative tumor necrosis and apoptotic bodies were frequently observed. Immunohistochemical study showed that CD20, the B-cell marker, was negative in all cases. The positivity rates for T-cell markers CD3epsilon, CD4, CD5 and CD8 were 100% (49/49), 7% (3/46), 8% (4/48) and 63% (29/46), respectively. Most cases were also positive for NK-cell marker CD56 (79% 42/53). All cases expressed cytotoxic granule-associated proteins TIA-1 and granzyme B. Only 17% (8/46) of the cases were positive for anti-apoptotic protein bcl-2. The proliferation index, as demonstrated by Ki-67 immunostain, varied: 30% (14/47) with a low Ki-67 expression level (< or = 29%), 28% (13/47) with a medium level (30%-59%) and 42% with a high level (> or = 60%). There was a significant positive correlation between the bcl-2 positive expression and a high Ki-67 expression level. In-situ hybridization for EBV-encoded RNA was positive in all cases. Amongst the 41 cases with clinical information available, 63.4% presented with Ann Arbor stage I to II. The performance status score was 1 in 87.8% cases. High lactate dehydrogenase level was demonstrated in some patients (31.8%). Amongst the 27 cases with follow-up data available, the median survival was 13 months. The overall 1-year, 2-year and 5-year survival rates were 52%, 31% and 20%, respectively. In general, cases with high proliferation index carried poor prognosis.

CONCLUSIONSEN-NK/TCL is a mature T-cell and NK-cell neoplasm which can be accurately diagnosed by histologic examination, immunohistochemical study and in-situ hybridization. The prognosis is usually not favorable. Proliferation index of the tumor represents an independent prognostic factor.