Mature T-Cell and Natural Killer-Cell Neoplasms With Leukemic Presentations

This chapter focuses on the mature T-/natural killer (NK)-cell neoplasms that predominantly manifest clinically as leukemia. These include T-cell large granular lymphocytic leukemia, Sézary syndrome and mycosis fungoides, adult T-cell leukemia/lymphoma, T-lymphotropic leukemia, and aggressive NK-cell leukemia. The chapter also discusses NK-large granular lymphocytic leukemia (aka chronic lymphoproliferative disorder of NK cells), leukemic presentation of other nodal- or extranodal-based T-/NK-cell lymphomas, and lymphocytic variant hypereosinophilic syndrome. These T-/NK-cell lymphoproliferations are mostly diseases of adults. The natural course of the disease, prognosis, and clinical management vary significantly according to disease types. Distinction of these entities depends largely on morphologic examination of peripheral blood films, immunophenotypic analysis of the tumor cell population, and correlation with clinical features. Molecular genetic data have shed new light on the understanding of these disease entities and impacted the classification and management.