- T-cell-LGL leukemia must meet all of the following criteria: CD3+ and CD57+ cells > 300/mm³ or CD8+ cells > 650/mm³ by phenotypic studies of peripheral blood, evidence for clonal T-cell receptor gene rearrangement based on positive flow cytometric analysis, T-cell receptor (TCR)-γ chain polymerase chain reaction (PCR), TCR-Vβ PCR, or by Southern blot analysis