TRISOMY-8 IN ACUTE PROMYELOCYTIC LEUKEMIA - AN INTERPHASE STUDY BY FLUORESCENCE IN-SITU HYBRIDIZATION

Acute promyelocytic leukaemia (APL) is characterized by t(15;17)(q24;q21), Trisomy 8 is the commonest accompanying karyotypic aberration, We investigated 14 APL patients for trisomy 8 using fluorescence in situ hybridization (FISH), Conventional cytogenetic analysis showed trisomy 8 in two of nine successfully karyotyped cases. With FISH, a possible third case showing a subclone (1-2 . 5%) with trisomy 8 was found. The trisomy 8 clone size defined by karyotyping and FISH was concordant in one case and discordant in another, in which trisomy 8 was found in 100% of metaphases but only in 48% of leukaemic protomyelocytes by FISH, Therefore trisomy 8 was mosaic in all the cases, suggesting that it had arisen from clonal evolution, All-trans-retinoic acid successfully induced morphologic remission in both cases with trisomy 8.