Spectrum of Clonal Large Granular Lymphocytes (LGLs) of αβ T Cells: T-Cell Clones of Undetermined Significance, T-Cell LGL Leukemias, and T-Cell Immunoclones.

OBJECTIVES: Clones of T-cell large granular lymphocytes (LGLTs) were detected by flow cytometry. Disease associations are described.

METHODS: Flow cytometry on blood or marrow detected clonal LGLTs by analyzing variable regions of the T-cell receptor β chain.

RESULTS: LGLT clones were detected in 20% (54/264) of tested patients. The clone sizes were less than 2.0 × 10(9)/L in the blood in 73% and less than 10% of marrow space in 94%. Blood counts showed cytopenias. Clinical associations included B-cell clones, myeloid neoplasms, nonneoplastic disorders of blood or marrow, transplants, systemic immune disorders, carcinomas, or hypothyroidism. Twelve patients had LGLT leukemia. Most (76%) had small LGLT clones with limited impact on the clinical management.

CONCLUSIONS: Most of the LGLT clones detected by flow cytometry were small and did not change the clinical management. We propose the following terminology: T-cell clones of undetermined significance, LGLT leukemias, and T-cell immunoclones.