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 malignancies has led to the need for a correlation between cytogenetic and morphological abnormalities. This study aimed to achieve this by the application of interphase cytogenetics to marrow trephine sections, a technique not previously reported for formatin fixed, paraffin wax embedded trephine biopsies. Methods - Dual colour fluorescence in situ hybridisation (FISH) was used to detect numerical and structural abnormalities in routinely processed paraffin 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 specific probes were hybridised with sections and disclosed by fluorescein isothiocyanate and rhodamine/Texas red labelled antidigoxigenin and antibiotin amplification; translocations were identified by colocalisation of probes using a double wavelength bypass filter. Results - A translocation signal was present in 12% and 11.5% of the cells counted in the t(8;21) and t(15;17) cases, respectively, but in none of the normal controls (p <0.001). In the case of trisomy 8, 9% of the cells counted 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 material, enabling it to be used as a research tool but also, and perhaps more importantly, in clinical practice.