[1490] Immunophenotypic Analysis of T-Cell Large Granular Lymphocytic (T-LGL) Leukemia and Chronic Lymphoproliferative Disorder of NK Cells (CLPD-NK)

Josette Ragheb, LoAnn Peterson, Yi-Hua Chen. Northwestern Memorial Hospital, Chicago, IL

Background: T-LGL leukemia and CLPD-NK are indolent lymphoproliferative disorders characterized by a persistent proliferation of clonal T-LGLs or NK cells in the peripheral blood without a clearly identified cause. Flow cytometric immunophenotyping and/or molecular analysis for T-cell receptor (TCR) gene rearrangement are commonly used in the evaluation of the diseases.
Design: Immunophenotype of 34 cases of T-LGL leukemia and 8 CLPD-NK was evaluated by flow cytometric analysis, including the common T-cell antigens, NK cell-associated antigens, cytotoxic molecule-associated antigens and killer inhibitory receptors (KIRs), and correlated with molecular analysis of TCR gene rearrangement.
Results: The age of the patients ranged from 38 to 90 years with a median age of 60; the male to female ratio was 19:23. In 34 cases of T-LGL leukemia, 30 (88%) were CD8+; 3 (9%) were CD4+CD8+ and 1 (3%) was CD4+. Eight of 34 cases (23%) were TCR-gamma/delta+. Loss of expression of CD5 (26/34; 76%) was the most common abnormality. The expression of CD16, CD56 and CD57 were detected in 12 of 31 (39%), 10 of 31 (32%) and 19 of 31 (61%) cases, respectively. TIA-1 and granzyme B were positive in 31/31 (100%) and 14/31 (45%) cases, respectively. The abnormal KIR expression was detected in 19 of 23 (83%) T-LGL leukemias, including 15 (65%) with restricted KIR expression and 4 (17%) with co-expression of 2 KIR molecules; the remaining 4 (17%) cases were negative for all three KIR molecules; however, they were positive for clonal TCR gene rearrangement. Clonal TCR gene rearrangement was detected in 23 of 24 (96%) cases of T-LGL leukemia and correlated with abnormal KIR expression. In 8 cases of CLPD-NK, abnormal KIR expression was detected in all patients, including lack of KIR molecules in 4 cases, restricted KIR expression in 2 cases and co-expression of 2 KIR molecules in 2 cases.
Conclusions: 1). T-LGL leukemia is an indolent disease typically derived from CD8+, TCR alpha/beta+ cytotoxic T cells; however, other variant such as TCR-gamma/delta+ T-LGL leukemia is not uncommon and should be differentiated from aggressive gamma/delta T cell lymphoma/leukemia. 2). In cases with negative expression of KIR molecules, PCR analysis for TCR gene rearrangement is important to determine clonality. 3). Loss of CD5 is the most common phenotypic abnormality, but CD57 expression is less frequent than was previously reported.
Category: Hematopathology

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 277, Tuesday Afternoon

 

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