Characterization of New Aberrations in 25 Splenic Marginal Zone B-Cell Lymphomas (SMZBCL) Using Spectral Karyotyping Technique (SKY).

BACKGROUND/INTRODUCTION

Splenic Marginal Zone B-Cell Lymphoma (SMZBCL) is a specific low grade small B-cell lymphoma described by the World Health Organization (WHO). SMZBCL has distinct features from other B-cell malignancies, but few studies include a large series of patients. Previous reports suggest that SMZBCL constitute a genetically heterogeneous disease being 7q22-q32 deletions and gains of 3q the most frequent cytogenetic aberrations. Karyotypes are often complex and difficult to interpret. Other recurrent chromosomes involved are 1 and 8. Nevertheless, at this cytogenetic level few studies have been reported and the possible chromosome markers are not still well defined.

OBJECTIVES

The aim of this study is to define karyotypes from patients with SMZBCL by SKY technique.

PATIENTS AND METHODS

Among a series of 138 patients we have selected 25 with undefined karyotype. The diagnosis of SMZBCL was confirmed by morphology, histology, phenotype and clinical data. All samples were obtained from peripheral blood, bone marrow or spleen. The current SKY protocol has been used with minor modifications to improve the spectral image. We analyzed a minimum of ten metaphases per karyotype and they were described according to the International System for Human Cytogenetic Nomenclature (ISCN).

RESULTS

All the studied karyotypes were complex with chromosome aberrations which, in most cases, were not fully characterized by G-banding. SKY has allowed to refine chromosomal aberrations and revealed new translocations which were not defined by conventional cytogenetics. In nine cases, the karyotype remained unchanged after SKY analysis and in the remaining cases, new aberrations were described.

We observed that the most common involved chromosomes in translocations were 14, 6, 13 and 17.

CONCLUSIONS

SKY provides a useful complementary technique to routine conventional cytogenetics in the analysis of lymphomas with complex karyotypes. SKY will permit to reveal new translocations associated with SMZBCL. The following new translocations involving 14q32 were found: t(1;14)(p22;q32), t(1;14)(q21;q32), t(9;14)(?;q32), t(9;14)(9pter-9p21::14q32-14q11::9p24-9qter), t(9;14)(p21;q32), t(10;14)(p12;q32), t(14;19)(q32;q13).