Dual colour FISH in paraffin wax embedded bone trephines for identification of numerical and structural chromosomal abnormalities in acute myeloid leukaemia and myelodysplasia

Aims/Background-The advent of new treatments for haematological malignancie s has led to the need for a correlation between cytogenetic and morphologic al abnormalities. This study aimed to achieve this by the application of in terphase cytogenetics to marrow trephine sections, a technique not previous ly reported for formalin fixed, paraffin wax embedded trephine biopsies. Methods-Dual colour fluorescence in situ hybridisation (FISH) was used to d etect numerical and structural abnormalities in routinely processed paraffi n wax embedded trephine biopsies. Three cases with t(8;21) and three with t (15;17) were analysed, together with a case of trisomy 8. Chromosome specif ic probes were hybridised with sections and disclosed by fluorescein isothi ocyanate and rhodamine/Texas red labelled antidigoxigenin and antibiotin am plification; translocations were identified by colocalisation of probes usi ng a double wavelength bypass filter. Results-A translocation signal was present in 12% and 11.5% of the cells co unted in the t(8;21) and t(15;17) cases, respectively, but in none of the n ormal controls (p < 0.001). In the case of trisomy 8, 9% of the cells count ed contained three hybridisation signals for chromosome 8, whereas no cell contained more than two in the normal control (p < 0.001). Conclusions-This technique is useful for archived routinely processed mater ial, enabling it to be used as a research tool but also, and perhaps more i mportantly, in clinical practice.