Fluorescent in situ hybridization (FISH) of chromosome 3q26 and 3q21 loci reveal hidden 3q26 aberrations. BAC clone localization from centromere (Cen) to telomere (Tel) (A). A metaphase from EVI1⁺ patient no. 28 revealed a cryptic inv(3)(q21q26) (inv3) and a normal chromosome 3 (nor3) using EVI1 (RP11-82C9) and MDS1 (RP11-141C22) (B) and RPN1 (RP11-456K4) BAC clones (C). Micrographs after FISH were acquired by imaging with a fluorescence microscope (Axio-Imager Z1; Zeiss, Sliedrecht, The Netherlands) fitted with a Plan-Apochromat at 100x/1.40 numeric aperture oil objective, a CCD video camera (Metasystems, Altlussheim, Germany), and using Isis software for capturing and processing fluorescent images (v5.1.7, Metasystems).