Leukemic involvement is a common feature in mantle cell lymphoma

BACKGROUND. The reported incidence of peripheral blood involvement in patients with mantle cell lymphoma (MCL) ranges from 13% to 77%. The aim of the study was to analyze the prevalence and the biologic and clinical significance of leukemic involvement in a series of patients with MCL. METHODS. Leukemic expression was assessed by conventional morphology and flow cytometry (FC) in 48 patients. In addition, comparative genomic hybridization (CGH) was performed in 27 patients. RESULTS. At diagnosis, 44 patients (92%) had evidence of leukemic expression by FC, including 8 patients (17%) without morphologically apparent leukemic involvement. Moreover, a lymphocyte count >= 5 X 10(9)/L was observed in 25 cases (52%). The most frequent imbalances detected by CGH were gains of 3q, 7p, 8q, 9q, 12q, and 13q, and losses of 13q, 1p, 9p, 11q, 10p, 17p, 6q, 8p, and 9q. Using a cutoff of 5 X 10(9)/L lymphocytes, cases with lymphocytosis more frequently presented with gains of 3q (P =.02), losses of 10p (P =.05), a low response rate (P -.04), and a short survival (P =.05). CONCLUSIONS. Leukemic expression at diagnosis detected by FC was found to be highly frequent in this series of patients with MCL. Although morphologically apparent leukemic expression was not associated with specific chromosomal alterations detected by CGH, a lymphocyte count >= 5 X 10(9)/L was correlated with particular genetic abnormalities and a poor outcome.