Differential diagnosis of leukemic T- and NK-cell neoplasms. ∗NK-LGLL differs from T-LGLL by the absence of expression of the TCR and lack of monoclonal TR rearrangement; the clonal neoplastic nature of this disorder is supported by a restricted activated KIRs expression and the presence of acquired mutations, especially in TET2, STAT3, and CCL22 (mostly exclusive). ANKL, aggressive NK-cell leukemia; BM, bone marrow biopsy; HPS, hemophagocytic syndrome; LN, lymphadenopathy; NK-LGLL, chronic LPD of NK cells/NK large granular lymphocytic leukemia; SS, Sezary syndrome; T-LGLL, T-cell large granular lymphocytic leukemia.