XIV. T- and NK-cell lymphoproliferative disorders

Mature T-cell and natural killer (NK)-cell neoplasms (Table 1) represent a heterogeneous spectrum of post-thymic T-celland NK-cell-derived malignancies. They represent 12% of all nonHodgkin lymphomas (NHLs). Significant geographic variation is noted with increased prevalence of select subtypes [i.e. adult T-cell leukemia/lymphoma (ATLL) and extranodal NK/T-cell lymphoma, nasal type] seen in Asian nations that may reflect exposure to etiologic agents such as human T-cell leukemia virus-1 (HTLV-1) and Epstein–Barr virus (EBV). The pathologic assessment of these cancers can be challenging and often requires immunophenotypic, cytogenetic and/or molecular analysis to ensure appropriate classification (Table 2). The most common entities will be discussed, highlighting clinical and pathologic manifestations, prognostic features and therapeutic strategies.