Mature NK and T-cell lymphomas are occasionally encountered in Asia but are very rare in Western populations. In part due to its rarity, little is known about this group of neoplasms, and despite being rather different disease entities, they are all treated similarly but with diverse clinical outcomes. Novel biomarkers (at both the genetic and protein levels) are needed to resolve diagnostic difficulties, improve prognostication and develop targeted therapies. To rectify this deficiency, we interrogated the transcriptome of several NK and mature T-cell lymphomas by whole-genome expression profiling for new markers that may further stratify this diverse group of conditions. Our initial efforts have identified a promising candidate marker that appears to differentiate NKTL lymphoma from other forms of T-cell neoplasms, and this finding has been validated by immunohistochemistry on archival material in a large number of patient cases.