An international research consortium has shed light on the role of circular extrachromosomal DNA (ecDNA) elements in the progression and treatment resistance of glioblastoma, the deadliest brain tumor. These 'rogue' DNA rings exist outside chromosomes and exacerbate oncogene amplification, fueling aggressive cancer growth and evasion of therapies. The findings offer novel insights into glioblastoma biology and may open avenues for targeted interventions aimed at ecDNA-associated mechanisms.