Large granular lymphocyte leukemia (LGL-L) is defined morphologically as a group of lymphoproliferative disorders, including T-cell large granular lymphocytic leukemia (T-LGL-L), chronic lymphoproliferative disorders of NK cells (CLPD-NK), and aggressive NK cell leukemia. We investigated the morphological features of LGL leukemic cells in LGL-L patients to identify screening methods best suited to application in daily clinical practice. LGL leukemic cells were mostly indistinguishable from normal LGL; however, we developed a simplified approach to distinguishing among these cells, in which lymphocyte % and the proportion of granular lymphocytes among lymphocytes (GL %) can serve as parameters at the cut-off values of 52 and 50 %, respectively. We confirmed the accuracy of these methods in validation groups. It may be useful to evaluate GL % to screen for LGL-L using a cut-off threshold of 50 when Lym % exceeds 52 in the peripheral blood examination in cases in which LGL-L is suspected in daily practice while keeping clinical context and the coefficient of variation of these parameters under consideration.
Keywords: Cytotoxic T-cell; Granular lymphocyte; LGL; Large granular lymphocyte leukemia; NK cell.