B- Prolymphocytic Leukemia Shows Heterogeneous IgVH Mutational Status and Expression of ZAP-70 and CD38.

Abstract

B-cell prolymphocytic leukemia (B-PLL) is a rare lymphoid leukemia with an aggressive course. Diagnosis is based on morphology (>55% peripheral blood prolymphocytes), immunophenotype and histology when available, as there is no cytogenetic hallmark for this disease. There are scanty data regarding the mutational status of the variable region of immunoglobulin heavy chain (IgVH) genes and ZAP-70 expression in B-PLL. Davi et al ( Blood 1996; 88:970–6) showed that 9 of 11 B-PLL cases had mutated IgVH genes (<98% homology) with a preferential use of the V3-23 and V4-34 genes, accounting for more than half of the B-PLL repertoire.We analyzed the mutational status of IgVH genes and ZAP-70 expression in 16 B-PLL cases and correlated the findings with clinical and biological features such as CD38 expression, chromosome abnormalities detected by FISH and overall survival. There were 7 females and 9 males, with a median age of 71 years (range 42–91). All except one were untreated at the time of the study. The diagnosis was established by peripheral blood morphology and immunophenotype (CLL score ≤ 3) in all cases and bone marrow and spleen histology in 6. Mantle cell lymphoma was excluded by the absence of t(11;14) by FISH in 12 out of 12 cases tested, including 4 which were CD5 positive. IgVH mutational status was performed by PCR (cut off >98% homology) and ZAP-70 expression was evaluated by 4-colour flow cytometry. Seven of 13 cases (54%) in which IgVH mutational status was evaluable, showed unmutated IgVH genes (99.7–100% homology) and 6 (46%) mutated IgVH genes (90.1–97.4% homology). V3-23 and V4-34 genes were used in one third of the cases. ZAP-70 was expressed (≥ 20% CD19+ cells) in 7 of 10 evaluable cases and CD38 (≥ 30% of CD19+ cells) in 7 of 11 cases. FISH analysis showed delp53 in 6/13 (46%) and del(13)(q14) in 3/11 (27%) cases; trisomy 12 was absent in 7 cases tested. Correlation between IgVH status and other features is shown in the table. There was a prevalence of delp53 (83%) among the unmutated group, while ZAP-70 expression did not correlate with IgVH mutational status. Median overall survival was 41 months. Six patients (4 mutated, 2 unmutated) are alive at 50 months (range 8-112) from diagnosis, 9 (5 unmutated and 2 mutated) died at 17 months (range 0–55) and 1 was lost to follow-up at 4 months. The number of patients is too small to conclude whether IgVH mutational status and/or ZAP-70 expression have a significant impact on survival. In summary, B-PLL is heterogeneous with respect to IgVH mutational status as in most chronic B-cell disorders, with equal representation of unmutated and mutated cases. P53 deletion is more common in the unmutated subgroup and most of the cases express ZAP-70 and CD38.Laboratory findings according to mutational statusZAP (>/=20%)CD38 (>/=30%)Del p53Del (13)(q14)Trisomy 12Unmutated (7)4/51/45/62/50/3Mutated (6)2/34/51/50/40/4