Scientists have uncovered evidence that a common form of brain cancer may begin developing years before a tumour becomes visible, originating in brain cells that appear completely normal. The discovery opens the door to earlier diagnosis and new treatment strategies aimed at preventing recurrence.

Researchers in South Korea found that IDH-mutant gliomas — brain tumours that often affect people under 50 — do not start when a tumour mass forms. Instead, the disease begins much earlier, when normal-looking brain cells acquire a silent genetic mutation and slowly spread through the brain’s cortex.

The study, published in Science, shows that Glial Progenitor Cells (GPCs) can pick up an IDH mutation long before any symptoms appear. Although these cells look healthy under a microscope, they quietly migrate through the brain, laying the groundwork for cancer years in advance. By the time a tumour is detected, mutated cells may already be widely distributed.

To uncover this hidden phase, the research team used spatial transcriptomics — an advanced technology that maps which genes are active and where — allowing them to detect cancer-related mutations in tissue that appeared normal to the naked eye.

The findings also highlight key differences between brain cancer subtypes. While earlier research showed that glioblastoma originates from neural stem cells, this study confirms that IDH-mutant gliomas arise from GPCs in the cerebral cortex, following a distinct biological pathway.

Animal experiments further supported the discovery, as introducing the same mutation into mouse GPCs reproduced critical steps of tumour development.

Experts say the research could transform how brain cancer is diagnosed and treated. By targeting the cells and regions where tumours truly begin — rather than only the visible mass — doctors may one day detect the disease earlier and reduce the risk of it returning.