CHROMOSOME-8 TETRASOMIES AND PENTASOMIES - A CLONAL ABNORMALITY CLOSELY ASSOCIATED WITH ACUTE MONOCYTIC LEUKEMIA

We report four cases of polysomy 8 (one tetrasomy and three pentasomie s) observed in acute monocytic leukemia (FAB M4 and M5). Three of them showed a rearrangement of 11q23 identified by conventional cytogeneti c analysis and/or chromosome painting. Our cases as well as a review o f the literature, suggest that polysomy 8 is preferentially associated with monocytic differentiation (24/31), These polysomies have been ob served in 21 de novo leukemias and in 10 secondary hematological disor ders. A 11q23 rearrangement has been detected in 9 out of 32 patients, by conventional cytogenetic techniques in 7 and by FISH in 2. We sugg est that these cases should be analysed by FISH and molecular studies in order to detect a rearrangement of MLL/11q23. Monocytic differentia tion is often associated with a change of the MLL gene and the polysom y 8 might be a particular clonal evolution secondary to 11q23 abnormal ity.