This study demonstrates the presence of double-stranded DNA (dsDNA) in exosomes, a novel biomarker with potential for early cancer detection and metastasis monitoring. Exosomes, small vesicles secreted by various cell types, contain functional biomolecules that can be transferred to recipient cells. The authors used enzymatic methods (dsDNA-specific shrimp DNase) and physical/structural studies (atomic force microscopy, AFM) to confirm the presence of dsDNA in exosomes. They found that exosomal DNA (exoDNA) represents the entire genome and reflects the mutational status of parental tumor cells. The study also showed that exoDNA can be used to detect tumor-specific genetic mutations, such as the BRAF(V600E) mutation in melanoma and EGFR mutations in non-small cell lung cancer. The findings suggest that exoDNA has significant translational potential as a circulating biomarker for cancer detection and treatment monitoring.This study demonstrates the presence of double-stranded DNA (dsDNA) in exosomes, a novel biomarker with potential for early cancer detection and metastasis monitoring. Exosomes, small vesicles secreted by various cell types, contain functional biomolecules that can be transferred to recipient cells. The authors used enzymatic methods (dsDNA-specific shrimp DNase) and physical/structural studies (atomic force microscopy, AFM) to confirm the presence of dsDNA in exosomes. They found that exosomal DNA (exoDNA) represents the entire genome and reflects the mutational status of parental tumor cells. The study also showed that exoDNA can be used to detect tumor-specific genetic mutations, such as the BRAF(V600E) mutation in melanoma and EGFR mutations in non-small cell lung cancer. The findings suggest that exoDNA has significant translational potential as a circulating biomarker for cancer detection and treatment monitoring.