Cytogenetic analysis of B cell chronic lymphoid leukemias classified according to morphologic and immunophenotypic (FAB) criteria.

609 patients with B cell chronic lymphoproliferative disorder were studied with the primary aim of analyzing the cytogenetic profile of B cell chronic lymphocytic leukemias and, if possible, define correlations with FAB classification of these diseases. Morphological and immunological studies were performed according to criteria proposed by the FAB group. A panel of monoclonal antibodies, including at least sIg, CD19, CD5, and FMC7 was used. Interpretations of morphology and cytogenetics were made independently. When applying strict FAB criteria 65% of the cases could be classified. Most of them (44%) were chronic lymphocytic leukemia (CLL). The cases not satisfying strict FAB criteria could be divided into two groups: one closely related to CLL, and here defined as atypical CLL (aCLL) (21%) and another group consisting of patients with leukemic manifestations of B cell non-Hodgkin's lymphoma (LL) (14%). Analyzable metaphases were obtained in 89% of patients. Clonal abnormalities were present in 35% of patients. The most frequent chromosomal changes were abnormalities of chromosome 11q (60 cases), trisomy 12 (46 cases) and structural rearrangements of chromosome 14q (44 cases). Statistical associations with FAB subtypes were found: aCLL and trisomy 12 (P < 0.00001); mantle zone lymphoma (MZL) and t(11;14) (P < 0.00001) and del(6)(q) (P < 0.0001); CLL/mixed cell type and del(6)(q) (P < 0.002); follicular lymphoma and t(14;18) (P < 0.00001); splenic lymphoma with villous lymphocytes and del(7)(q) (P < 0.0004); leukemic lymphoma (LL) with rearrangements in chromosome 9q (P < 0.0001) and trisomy of 3 (P < 0.001). Chronic lymphocytic leukemia was not statistically associated with any specific chromosomal abnormality. However, this subtype showed a high incidence of del(11)(q) and rearrangements of 13q. This study confirms the value of cytogenetic investigation in the diagnosis of these disorders and may provide some new elements for future refinement of the FAB classification in mature B cell lymphocytic disorders.