For both methods, paraffin tissue sections are cut on a microtome at 5 microns and placed onto silanized slides. Slides are allowed to air dry, preferably overnight. Cut sections should not be stored for greater than 6 weeks before testing. A minimum of 4 hours drying time is required. Bake all slides overnight at 56° C before staining for FISH.
By comparison to the hematoxylin and eosin (H&E) method, slides should be marked for the tumor area of interest on the underside of the slide using a diamond tipped pen prior to beginning. This will ensure that enough tumor cells are present on the slide before the assay is performed.