RESUMO
Expression of myeloid or T cell lymphoid in precursor B cell acute lymphoblastic leukemia [pre-B cell ALL], which is referred to as aberrant expression, is quite a common phenomenon. CD66c is a myeloid marker which has aberrant expression in pre-B cell ALL, with strong correlation with non-random genetic changes [BCR/ABL rearrangement]. Another leukemia associated marker [CD25] is frequently expressed in pre-B cell ALL. The frequency of CD25-expressing lymphoblasts has been found to be significantly higher in BCR/ABL-positive vs. BCR/ABL-negative patients. In a cohort of 103 patients diagnosed with pre-B cell ALL or biphenotypic leukemia and studied for expression of CD66c and CD25 at presentation, we evaluated the frequency of expression of either or both in BCR/ABL positive cases. Surface CD66c was expressed by 70 cases [68%] and CD25 was expressed by 33 cases [32%] while both were expressed together on 29 cases [28%]. BCR/ABL was positive in 18/103 patients. All BCR/ABL positive cases were positive for surface CD66c and CD25. Positivity for both leukemia-associated antigens CD66c and CD25 in combination can predict the presence of BCR/ABL rearrangement in pre-B cell ALL. While this finding does not replace the detection of BCR/ABL abnormality by cytogenetic or molecular techniques, it does provide an early and handy tool for prediction and management of high-risk cases of pre-B cell ALL, especially in centers with limited laboratory facilities