to a board-certified cytogeneticist for review, and to write an interpretation taking into account the patient's previous history and other clinical findings. the results are then given out reported in an international system for human cytogenetic nomenclature 2009 (iscn2009).. fluorescence in situ hybridization interphase cells positive for a t(9;22) rearrangement fluorescence in situ hybridization (fish) refers to using fluorescently labeled probe to hybridize to cytogenetic cell preparations. in addition to standard preparations fish can also be performed on: bone marrow smears blood smears paraffin embedded tissue preparations enzymatically dissociated tissue samples uncultured bone marrow uncultured amniocytes cytospin preparations slide preparation this section refers to the preparation of standard cytogenetic preparations the slide is aged using a salt solution usually consisting of 2x ssc (salt, sodium citrate). the slides are then dehydrated in ethanol, and the probe mixture is added. the sample dna and the probe dna are then co-denatured using a heated plate and allowed to re-anneal for at least 4 hours. the slides are then washed to remove the excess unbound probe, and counterstained with 4',6-diamidino-2-phenylindole (dapi) or propidium iodide. analysis analysis of fish specimens is done by fluorescence microscopy by a clinical laboratory specialist in cytogenetics. for oncology, generally, a large number of interphase cells are scored in order to rule out low-level residual disease, generally between 200 and 1,000 cells are counted and scored. for congenital problems usually 20 metaphase cells are scored. future of cytogenetics advances now focus on molecular cytogenetics including automated systems for counting the results of standard fish preparations and techniques for virtual karyotyping, such as comparative genomic hybridization arrays, cgh and single nucleotide polymorphism arrays.