CD79b expression in chronic lymphocytic leukemia: Association with trisomy 12 and atypical immunophenotype

Context - CD79b is a relatively newly characterized B-cell marker that is expressed in a minority of chronic lymphocytic leukemia (CLL) cases. Objective - To systematically correlate CD79b expression with specific morphologic and immunophenotypic findings and trisomy 12. Design - We assessed CD79b expression in 100 consecutively accrued CLL cases that were also analyzed by conventional cytogenetics. Based on the association between trisomy 12 and CD79b expression, we then assessed 43 additional CLL cases with trisomy 12. CD79b expression was correlated with morphology and expression of other immunophenotypic markers. Results - Eighteen (18%) of 100 consecutively accrued cases were CD79b positive. No significant association was found between CD79b expression and atypical morphology. CD79b expression correlated with CD22 and FMC7 positivity. Eight (8%) cases had trisomy 12; 4 (50%) of these were CD79b positive, suggesting an association with trisomy 12. Examination of a second group of 51 CLL cases with trisomy 12 (including 8 cases from the initial study group) showed that CD79b was positive in 26 cases (49%), a frequency significantly higher than that of the consecutively accrued CLL cases without trisomy 12 (P < .05). Conclusions - We conclude that CD79b immunoreactivity is positive in approximately 20% of CLL cases and that expression correlates with trisomy 12 and atypical immunophenotypic findings.