ACUTE LYMPHOBLASTIC LEUKEMIAS WITH DELETION OF 11Q23 OR A NOVEL INVERSION (11)(P13Q23) LACK MLL-GENE REARRANGEMENTS AND HAVE FAVORABLE CLINICAL-FEATURES

Balanced translocations affecting the 11q23 region are among the most frequent chromosomal abnormalities in childhood acute lymphoblastic le ukemia (ALL), comprising 5% to 6%. These cases consistently have a rea rranged MLL gene and are associated with high-risk presenting features , hyperleukocytosis and younger age, and a poor treatment outcome. To assess the clinical and biologic significance of 11q23-associated stru ctural chromosomal abnormalities other than translocations, we studied 17 cases of childhood ALL [14 with del(11)(q23) and 3 with inv(11)(p1 2q23)] that were identified among 785 cases with successful chromosome analysis. In contrast to reported cases with 11q23 and MLL gene rearr angement, our series was characterized by relatively low leukocyte cou nts (median, 15.1 x 10(9)/L), expression of CD10 antigen but not myelo id-associated CD15 and CDw65 antigens, a relatively high frequency of T-cell immunophenotypes, and a generally favorable prognosis. All 13 c ases with interpretable molecular analysis lacked MLL gene rearrangeme nts. We suggest that most cases with deletions or inversions affecting the 11q23 region represent clinically and biologically different enti ties as compared with those defined by 11q23 translocation. (C) 1995 b y The American Society of Hematology.