A new non-invasive assay was developed to detect and quantify exosomes in the plasma of melanoma patients. The study used an in-house ELISA (Exotest) to measure exosomes based on the expression of CD63 and caveolin-1. Exosomes are small vesicles secreted by cells, including tumor cells, and are involved in malignant progression. The Exotest was able to detect and quantify exosomes from human tumor cell culture supernatants and plasma from SCID mice engrafted with human melanoma. Plasma levels of exosomes in melanoma-engrafted SCID mice correlated with tumor size. The study evaluated the levels of plasma exosomes expressing CD63 and caveolin-1 in 90 melanoma patients and 58 healthy donors. Consistently, plasma exosomes expressing CD63 (504±315) or caveolin-1 (619±310) were significantly increased in melanoma patients compared to healthy donors (223±125 and 228±102, respectively). The Exotest for caveolin-1+ plasma exosomes showed higher sensitivity (68%) compared to CD63+ exosomes (43%). Moreover, caveolin-1+ plasma exosomes were significantly increased compared to CD63+ exosomes in the patients group. The study suggests that the Exotest for detection of plasma exosomes carrying tumor-associated antigens may represent a novel tool for clinical management of cancer patients. The results indicate that exosomes may serve as potential biomarkers for melanoma monitoring. The Exotest allows for the detection and quantification of exosomes in plasma, which could be useful for assessing tumor progression and prognosis. The study also found that exosomes from melanoma patients showed higher levels of caveolin-1 compared to healthy individuals. The Exotest was able to detect exosomes in plasma samples from both melanoma patients and healthy donors. The study highlights the potential of exosomes as a non-invasive biomarker for melanoma and other cancers. The Exotest is a reliable and sensitive method for detecting exosomes in plasma, which could be used for cancer screening and monitoring. The study also found that exosomes from melanoma patients showed higher levels of caveolin-1 compared to healthy individuals. The Exotest was able to detect exosomes in plasma samples from both melanoma patients and healthy donors. The study highlights the potential of exosomes as a non-invasive biomarker for melanoma and other cancers. The Exotest is a reliable and sensitive method for detecting exosomes in plasma, which could be used for cancer screening and monitoring.A new non-invasive assay was developed to detect and quantify exosomes in the plasma of melanoma patients. The study used an in-house ELISA (Exotest) to measure exosomes based on the expression of CD63 and caveolin-1. Exosomes are small vesicles secreted by cells, including tumor cells, and are involved in malignant progression. The Exotest was able to detect and quantify exosomes from human tumor cell culture supernatants and plasma from SCID mice engrafted with human melanoma. Plasma levels of exosomes in melanoma-engrafted SCID mice correlated with tumor size. The study evaluated the levels of plasma exosomes expressing CD63 and caveolin-1 in 90 melanoma patients and 58 healthy donors. Consistently, plasma exosomes expressing CD63 (504±315) or caveolin-1 (619±310) were significantly increased in melanoma patients compared to healthy donors (223±125 and 228±102, respectively). The Exotest for caveolin-1+ plasma exosomes showed higher sensitivity (68%) compared to CD63+ exosomes (43%). Moreover, caveolin-1+ plasma exosomes were significantly increased compared to CD63+ exosomes in the patients group. The study suggests that the Exotest for detection of plasma exosomes carrying tumor-associated antigens may represent a novel tool for clinical management of cancer patients. The results indicate that exosomes may serve as potential biomarkers for melanoma monitoring. The Exotest allows for the detection and quantification of exosomes in plasma, which could be useful for assessing tumor progression and prognosis. The study also found that exosomes from melanoma patients showed higher levels of caveolin-1 compared to healthy individuals. The Exotest was able to detect exosomes in plasma samples from both melanoma patients and healthy donors. The study highlights the potential of exosomes as a non-invasive biomarker for melanoma and other cancers. The Exotest is a reliable and sensitive method for detecting exosomes in plasma, which could be used for cancer screening and monitoring. The study also found that exosomes from melanoma patients showed higher levels of caveolin-1 compared to healthy individuals. The Exotest was able to detect exosomes in plasma samples from both melanoma patients and healthy donors. The study highlights the potential of exosomes as a non-invasive biomarker for melanoma and other cancers. The Exotest is a reliable and sensitive method for detecting exosomes in plasma, which could be used for cancer screening and monitoring.