NK-cell Large Granular Lymphocyic leukemia (NK-LGL) / chronic NK cell lymphocytosis

Medium sized lymphocyten with abundant pale cytoplasm. They can not be distinguished from normal reactive NK-lymphocytes by morphology. Secondary benign NK-LGL expansion can be found in association with myelodysplastic syndrome and solid tumors.
In healthy blood samples the number of LGL-cells comprise 10 to 15 percent of peripheral blood lymphocytes; the absolute number is 200 to 400/µL.
Only about 5% of the LGL expansions is from NK origin. Patients often present with chronic neutropenia and anemia (but less severe as in T-LGL), hepatosplenomegaly and/or lymphadenopathy are rare.
By flowcytometry the cells typically show negative for CD3, CD4, CD5 and positive for CD2, CD16, CD56.