Fulminant clonal expansion of large granular lymphocytes: Characterization of their morphology, phenotype, genotype, and function

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Abstract
A 39-year-old woman exhibited abrupt malignant transformation of the large granular lymphocytes (LGL) after a chronic course of Tγ-lymphoproliferative disease (Tγ7-LPD). The Tγ-lymphocytes were CD2+, CD3-, CD8-, CD16+, Leu7-, and Leul9+ with morphologic characteristics of LGL. Newly appearing LGL were much larger and had more prominent azurophilic granules. Although fundamentally they had the same phenotype as the LGL in chronic stage, they showed increased la-like antigen and decreased CD16 antigen expressions. Immunoglobulin (Ig) G-kappa type monoclonal component was detected in the patient's serum. The LGL showed a germ-line configuration for T-cell receptor (TCR) beta and gamma chain genes, whereas the clonal chromosomal abnormalities indicated the neoplastic nature of the LGL. The LGL exhibited competent natural killer (NK), interleukin 2 (IL2) activated killer (AK), and antibody-dependent cell-mediated cytotoxicity (ADCC) activities. The LGL may have derived from NK cells at their mature stage with prethymic phenotype and may have influenced the homeostasis of the patient's humoral immune response.