Fluorescence In SituHybridization (FISH) Reveals Unexpected Cryptic Chromosome 11 Defects in MDS/AML Patients.

Conventional cytogenetics (CC) discovers clonal chromosomal defects in about 40–80% of de novoMDS/AML. However, due to the poor quality of metaphases, CC is often unable to reveal cryptic defects, precisely define chromosomal breakpoints and establish the nature of marker chromosomes. All these drawbacks may be overcome by FISH, a powerful technique with high sensitivity and specificity. Abnormalities of chromosome 11 long arm and of band 11p15 are seen in 5–7% and in 0.5% of de novoMDS/AML. Herein we report two patients diagnosed as AML evolved from MDS. On CC the karyotype of the first patient was 47,XX,+3,t(15;20)(q15;p11),add(11)(p15) [20] [case 1] and that of the second patient was 45,XX,t(1;?)(q12;?),−5,−7,+8,add(11)(q23),add(12)(p13),add(17)(p13),add(21)(q22) [7]/46,XX,t(1;?)(q12;?),add(5)(q11),−7,+8,add(17)(p13),add(21)(q22) [8] [case 2]. In both the patients FISH was performed with commercial probes (LSI and TCP from Vysis and QBiogene, applied following manufacturer's guidelines) and Bacterial Artificial Chromosome (BAC) probes (kindly provided by the Wellcome Trust Sanger Institute, Cambridge UK) in order to better define chromosome 11 rearrangements. The BAC probes were cultured in LB broth for a night and the following day the DNA was extracted after lysis. Labelling with biotin and digoxigenin was carried out by nick translation reaction. Signal detection was obtained by fluorescein avidin and anti-digoxigenin.