TRANSLOCATION (12;21) "A RECENT PROGNOSTIC CYTOGENETIC ABNORMALITY IN PEDIATRIC B-CELL PRECURSOR (BCP) ACUTE LYMPHOBLASTIC LEUKEMIA"

Abstract

ALL is the most common form of childhood leukemia. Several factors including genetic changes, in particular chromosomal translocation has yielded a wealth of information on the mechanism of leukemogenesis, disease prognosis, monitoring the patient response to treatment and predicting MRD. In the current study, cytogenetic analysis was dorie on 25 children suffering from BCP-ALL by both conventional cytogenetic analysis (G-banding) and by FISH using LSI probe for detection oft(l2;21). Successful karyotyping was encountered in I 'J/25 (76%) patients with failure of mitosis in 6 (24%) patients. Both numerical and structural chromosomal aberrations were detected in II /I C) ( 57.8%) patients. Massive hyperdiploidy (>50 chromosomes) was encountered in 2/1 C) (I 0 5%) patients and was associated with better prognosis than other patients with hvpodiploidy 5/19 (26.3%) or structural aberrations in 5/19 (26.3%) patients. Metaphase and interphase FISH analysis of ALL patients revealed positive detection of t( 12;21) in 6 (24%) patients, one of them was associated with del( 12) detected by f-ISH, while conventional karyatyping revealed hyperdiploidy and del (3q) & del ( 13q) in two patients. More over FISH analysis allowed detection of trisomy 21 in one (4%) case. Follow up of the six positive cases fort ( 12;21) by FISH, revealed negative results in 5/6 (83.3%) patients while the last one (16.7%) remained positive. The patient experienced relapse 3 months after achieving remission despite absence of any landmark of hematological relapse at time FISH analysis. nSH technique provides a simple, rapid. specific and reliable methods for detecting chromosomal aberration not only in metaphase but also in interphase where conventional cytogenetic analysis could not be applied.