The exosomes containing tumor-specific protein represent a valuable source of material for the non-invasive diagnosis of malignant neoplasms. The exosomes from plasma and cell-associated exosomes from blood of healthy women, the patients with mastopathy and breast cancer patients were studied with the nanoparticle tracking analysis, transmission electron microscopy, flow cytometry and protein profiling. The exposure of CD63, CD24, CD9, and CD81 demonstrates isolation of mainly exosomes. A major part of exosomes in the blood of healthy women, patients with mastopathy and breast cancer patients is shown to be associated with the surface of blood cells. The concentration of the exosomes in the plasma of the breast cancer patients is higher than in the healthy women's plasma. The proteins ranged from 10 to 250 kDa were found in the exosomes by gradient SDS PAAGE; 8 regions of electrophoregram differ between healthy and illness patients in the expression level and number of proteins. These proteins are planned to be identified by MALDI TOF and studied as potential breast cancer markers.