The researchers used data from the Pan-Cancer project and The Cancer Genome Atlas (ICGC) to create tumour development timelines for several cancer types including glioblastoma, and colorectal and ovarian adenocarcinoma. Their findings suggest that tumour development can span the entire lifetime of an individual, so the mutations that initiate cancer progression may arise decades before diagnosis.

"We've observed that changes in chromosome count within tumour cells typically occur late during tumour evolution. However, in some cases, such as in glioblastoma multiforme tumours, these changes can occur decades before diagnosis," says Stefan Dentro, Postdoctoral Fellow at EMBL-EBI. "Typically, cells don't survive for very long with an odd number of chromosomes, but somehow these cells do; possibly founding a tumour that is detected many years later."

https://www.sciencedaily.com/releases/2020/02/200206080451.htm