Ovarian cancer is a silent killer. Early stage ovarian cancer is difficult to diagnose because most symptoms are subtle and thus of little use in diagnosis. As a result, the diagnosis is rarely made until the cancer spreads and advances to later stages. If diagnosed and treated in an early stage, ovarian cancer is often curable. However, when diagnosed in a late clinical stage, ovarian cancer is associated with a 5-year survival of only 35%. Early detection is key to reducing ovarian cancer-associated deaths. 

Tumor-derived extracellular vesicles (EV), nanometer-sized membrane vesicles which contain proteins, lipids, and nucleic acids, enter the circulation and as such their quantification and characterization may enable the diagnosis of cancer. The molecular content of EV is a fingerprint of the releasing cells and they are enriched for highly selected biomarkers which otherwise would consitute only a very small proportion of the total molecular blood content. The feasibility of blood-based EV protein biomarkers to diagnose early lesions of cancer is recently demonstrated for pancreatic cancer.