Extrachromosomal DNA in Oncology: History of Discovery, Research Methods, and Current Perspectives.

Extrachromosomal DNA (ecDNA) refers to circular DNA molecules without centromeres that are often found in the nuclei of cancer cells. The presence of ecDNA is associated with the development of drug resistance and poor disease prognosis. Although ecDNA was discovered 60 years ago, technological advances of the past decade have dramatically expanded our understanding of its biological significance and revealed a far greater role in cancer development than previously recognized, thus driving a rapid increase in research interest. This review describes the milestones in the history of ecDNA research and summarizes the current state of knowledge as of 2025. It provides a comprehensive overview of the mechanisms underlying ecDNA formation, organization, and functions, describes the principal methods used for ecDNA detection and analysis, and discusses its clinical relevance, as well as future directions in ecDNA research.