ABSTRACT
While the clinicopathologic and phenotypic features of nasal=nasal type NK=T-cell lymphomas and aggressive NK cell leukemia=lymphoma are well characterized (1,2) there is a considerable heterogeneity-–clinical as well as histological and immunophenotypic-–among other extranodal NK=T-cell lymphomas (3). In addition, the nomenclature shows overlaps and contradictions, making comparison of cases and delineation of characteristic features difficult. The unifying feature is expression of CD56 by tumor cells. The majority of cases also express cytotoxic proteins and some are EBV-positive.
