13q14 deletions are not primary events in B-cell chronic lymphocytic leukemia: a study of 100 patients using fluorescence in situ hybridization.

Fluorescence in situ hybridization with a chromosome 12-specific alpha-centromeric probe and a 13q14 yeast artificial chromosome probe was performed on interphase cells from 100 patients with B-cell chronic lymphocytic leukemia. Thirty-one patients exhibited a 13q14 deletion. No correlation was found between 13q14 deletions and clinical stage, sex, or morphology. Sixteen patients had trisomy 12, including 6 (of 12) with an atypical morphology. Trisomy 12 and 13q14 abnormalities were detected concomitantly in three patients only. The analysis of patients with deletions clearly showed that in five cases a significant number of cells retained two signals with the yeast artificial chromosome probe, indicating a genetic heterogeneity among the leukemic population. Our data confirm that the 13q14 deletion is a frequent event, indicate that the concomitant occurrence of 13q14 deletion and trisomy 12 is rare but possible, and show that both abnormalities are secondary events in B-cell chronic lymphocytic leukemia.