The incidence of trisomy 3 in splenic lymphoma with villous lymphocytes: a study by FISH

Splenic lymphoma with villous lymphocytes (SLVL) is a low-grade B-cell lymphoproliferative disorder characterized by splenomegaly and circulating villous lymphocytes. The relationship between SLVL and splenic marginal zone lymphoma (SMZL), a disorder with identical splenic histology to SLVL, is not clear. Previous studies have failed to show a consistent karyotypic abnormality in SLVL whereas trisomy 3 has been reported in patients with SMZL. The presence of trisomy 3 in SMZL and its absence in SLVL has been viewed as evidence that these are different diseases. However, it is possible that the frequency of trisomy 3 in SLVL has been underestimated because previous studies have relied on conventional cytogenetics. We have therefore used interphase fluorescence in situ hybridization (FISH) to re-assess the frequency of trisomy 3 in SLVL. We studied 70 patients, who were stratified into four groups according to the percentage of circulating villous lymphocytes. Trisomy 3 was found overall in 17% of patients. In particular, trisomy 3 was detected in 13% of cases with >50% of villous lymphocytes and which were considered typical of SLVL. In conclusion, we have demonstrated that some patients with SLVL have circulating cells with trisomy 3, which does not support the view that SLVL and SMZL are different diseases on the basis of the incidence of trisomy 3.