Extracellular vesicles as biomarkers in cancer diagnosis and prognosis

Extracellular vesicles (EVs) have emerged as key mediators in cancer biology, playing critical roles in intercellular communication within the tumor microenvironment. These nano-sized particles carry diverse molecular cargos, including proteins, lipids, DNA, and various RNA species, which reflect the biological state of their cells of origin. This chapter provides a comprehensive overview of the diagnostic and prognostic potential of EVs across a wide spectrum of tumor types, following the World Health Organization (WHO) tumor classification. We discuss the contribution of EVs in genetic tumor syndromes, solid tumors (such as skin, breast, digestive, and thoracic cancers), hematolymphoid malignancies, and pediatric cancers. Special emphasis is placed on the utility of EVs in liquid biopsy applications, offering minimally invasive alternatives for early diagnosis, monitoring of disease progression, treatment response, and detection of relapse. Furthermore, the chapter highlights specific EV-associated biomarkers, including proteins, microRNAs, long non-coding RNAs, and circular RNAs, identified in various biofluids such as blood, urine, saliva, and cerebrospinal fluid. Despite the promising potential of EVs as clinical tools, several challenges remain, including standardization of isolation and characterization methods, biological heterogeneity of EV populations, and the need for large-scale validation studies. Addressing these hurdles will be critical for the successful translation of EV-based biomarkers into routine oncology practice.