Frequent deletions of 6q23-24 in B-cell non-Hodgkin's lymphomas detected by fluorescence in situ hybridization

Deletions of the long arm of chromosome 6 (6q) are among the most frequent chromosome aberrations in malignant lymphomas and often occur as secondary changes in addition to typical translocations, such as t(14;18). Using fluorescence in situ hybridization (FISH) with two YAC probes hybridizing to 6q23-24 and with the centromeric probe D6Z1 as internal control, we studied 31 cases of low-grade and eight cases of high-grade B- cell lymphoma. Deletions of 6q23-24 were detected in 21 patients (56.8%) by FISH, compared to 13 patients (33.3%) by chromosome analysis. Deletions of 6q23-24 were found by FISH in 5 of 13 cases of small lymphocytic lymphoma, in 2 of 3 cases of mantle cell lymphoma, in 10 of 14 cases of t(14;18) positive low-grade follicular lymphoma, and in 4 of 8 cases of high-grade follicular lymphoma. This study shows that deletions of 6q23-24 are more frequent in B- cell lymphomas than previously suggested and that they can be detected more sensitively by FISH than by chromosome analysis. Contrary to previous reports indicating that the region 6q23-24 is preferentially deleted in low-grade lymphomas without t(14;18), our results indicate that deletions of 6q23-24 appear to be common in other pathological subsets of B-cell lymphoma as well, especially in follicular lymphomas with t(14;18).