Large Granular Lymphocyte Proliferation with the Natural Killer-Cell Phenotype

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Abstract
Lymphoproliferated disorders involving large granular lymphocytes (LGL) can be divided into a common T-cell subset (CD3+, CD8+) and a rarer natural killer (NK)-cell subset (CD2+, CD3−). The immunophenotype, clinical pathologic features, and cytogenetic and molecular genetic analyses are reported for seven patients with NK-cell-LGL proliferation. The typical immunophenotype was CD2+, CD3−, CD4−, CD11b+, and CD16+ or CD56+. A low but variable percentage of cells were CD8+ or CD57+. Unusual phenotypes with CD2− (1 of 7), CD11b− (1 of 7), or CD16−/CD56− (1 of 7) cells were seen. Strong NK-cell activity was observed in all cases, indicating that none of the NK-cell markers (CD11b, CD16, CD56, CD57) is essential for NK-cell activity. One patient died shortly after diagnosis from coexistent refractory multiple myeloma and another patient died within 1 month from the LGL proliferation. The other patients had been followed for 12 to 70 months, with a median followup period of 38 months. There was no progression of their LGL proliferation. Lymphocyte counts varied from 3.3 × 103/μL to 58.4 × 103/μL at the time of diagnosis. Unexplained anemia and neutropenia were observed in one patient. Cytogenetic abnormalities were detected in two of four patients studied with t(6;12) in one and der(5), der(6), and der(ll) in the other. The ~Tγ and Tβ genes were in the germline configuration and Epstein- Barr virus DNA was undetectable in five of five patients studied. Natural killer-cell LGL proliferations were morphologically indistinguishable from T-cell LGL proliferations. However, the two were immunophenotypically and genotypically distinct and NK-cell activity was consistently observed in the former. Most of the NK-cell proliferations also were chronic indolent disorders and the incidence of associated cytopenias seemed to be lower than T-cell LGL proliferations.

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