12Q13, A NEW RECURRENT BREAKPOINT IN ACUTE NONLYMPHOBLASTIC LEUKEMIA

The karyotypes of 312 successfully analyzed samples of children with a cute non-lymphoblastic leukemia (ANLL), which were sent to us by 72 Ge rman hospitals, were examined in order to find new recurrent chromosom e abnormalities of possible clinical relevance. Whereas most of the pa tients had one of the specific aberrations of ANLL or a normal karyoty pe, random numerical or structural changes were found in 61 children ( 20%). Four of them showed an abnormality involving band 12q13: t(12;17 )(q13;q21), t(12;21)(q13;q21), t(2;12)(p13;q13), and t(5;12)(p11;q13). Despite the fact that FAB subtypes were different (MO, M1 M6, AHL), t he blasts of all patients were characterized by immaturity and were di fficult to classify. The breakpoint 12q13 might be of clinical importa nce in ANLL, because the four patients in our study, as well as the 21 patients with this aberration found in the literature, had a very poo r prognosis.