Detection and validation of increased VEGFA gene copy number by FISH in OS. Using FISH detection, orange represents VEGFA probe signal (red arrows) and therefore VEGFA copy number, whilst green represents CEP 6 reference probe signal located in the centromere of chromosome 6 (green arrows). When VEGFA/CEP 6 signal ratios were equal to or higher than 1, and when more than two gene copies of VEGFA were found per cell in more than 90% of OC cells, increased VEGFA gene copy number was recorded. Two patterns of increased VEGFA copy number exist in OS, focally or in larger fragment forms (polysomy). A: No copy number aberration of VEGFA gene, B: focally increase VEGFA gene copy number, C: increased copy number of VEGFA gene in larger fragment form (polysomy).