Primary Cutaneous NK/T-cell lymphoma, nasal type and cd56-positive peripheral t-cell lymphoma A cellular lineage and clinicopathologic study of 60 patients from Asia

Primary cutaneous, extranodal natural killer/T-cell lymphoma, nasal type (PC-ENKTL), is a rare Epstein-Barr virus (EBV)-associated neoplasm with poorly defined clinicopathologic features. We performed a multinational retrospective study of PC-ENKTL and CD56-positive EBVnegative peripheral T-cell lymphoma (PC-CD56+PTCL) in Asia in an attempt to elucidate their clinicopathologic features. Using immunohistochemistry for T-cell receptors (TCRs), in situ hybridization for EBV, and TCR gene rearrangement, we classified 60 tumors into 51 with PC-ENKTL (20 of NK-cell, 17 T-cell, and 14 indeterminate lineages) and 9 with PCCD56+ PTCL. Tumors of T-cell origin accounted for 46% of PC-ENKTLs with half of these cases being TCR-silent. As compared with T-lineage tumors, PC-ENKTLs of NK-cell lineage had more frequent involvement of regional lymph nodes and more frequently CD8-negative and CD56-positive. Cases of PC-ENKTL showed more frequent tumor necrosis, younger age, and a higher frequency of CD16 and CD30 expression than cases of PC-CD56+PTCL. CD56-positive T-lineage PCENKTL tumors (n=8) had more localized disease in the TNM (tumor-node-metastasis) staging and were more often of gd Tcell origin compared with cases of PC-CD56+PTCL (n=9). PC-ENKTLs and PC-CD56+PTCLs were equally aggressive, with a 5-year overall survival rate of 25%. Tumor necrosis and CD16 expression may serve as useful surrogates for differentiating PC-ENKTL from PC-CD56+PTCL. A single lesion, an elevated lactate dehydrogenase level, and the presence of B symptoms were independent poor prognostic factors for PCENKTL in multivariate analysis. Further studies with more cases are warranted to delineate the clinicopathologic features and significance of EBV in these rare lymphomas.