Inactivation of A20 by mutation and deletion. (A) Representative chromatograms of A20 exon 7 genomic sequences obtained by direct sequencing of tumor and matched normal DNA from a nodal MZL (case 18-C), with a 1-bp somatic insertion leading to a frameshift. Positions according to reference sequence NM_006290.2. (B) Dual-color FISH analysis of an extranodal MZL (case 9-C), hybridized with A20 probes (red) and a chromosome 6 centromeric probe (green). Red arrows indicate cells with homozygous A20 deletions; white arrows point to cells with a normal signal pattern. (Three hundred cells were analyzed, fluorescence signals were captured after staining with 4′-6-diamidino-2-phenylindole [DAPI] using the Cytovision Imaging System [Applied Imaging, Santa Clara, CA] attached to a Nikon Eclipse 600 microscope 100×/1.40 NA oil objective [Nikon Instruments, Melville, NY.])