While primary breast cancer (BC) is often effectively managed, metastasis remains the primary cause of BC-related fatalities. Gaps persist in our understanding of the mechanisms underlying cancer cell predilection for specific organs (organotropism). Unraveling these mediators of site-specific metastasis could enhance early detection and enable more tailored interventions. Liquid biopsy represents an innovative diagnostic approach in cancer involving the non-invasive analysis of biological materials found in body fluids like blood or urine. These materials include circulating tumor cells, cell-free circulating tumor DNA, and tumor-derived extracellular vesicles (EVs), which offer valuable insights for characterizing and monitoring tumor genomes to advance personalized medicine. EVs, lipid-bound particles released from cells into the extracellular space, facilitate intercellular communication by transporting proteins and DNA (EV-DNA) implicated in cancer progression and organ-specific metastasis. The aim of this study was to conduct an in-depth analysis of cell-free DNA (cfDNA) and EVs using a murine model of BC cell lines with distinct metastatic potentials and organotropisms (lung, bone, liver, brain). We characterized the secretome of 8 different metastatic cell lines originating from the same parental non metastatic and metastatic cell line, as well as normal mammary epithelial cells to identify unique biomarkers specific to metastatic sites. Using ultracentrifigcation, we isolated small EVs ranging from 78.9 to 101nm isolated from the conditioned media of the cell lines. We confirmed the presence of established EV markers, including CD81, TSG101 and syntenin. Transmission electron microscopy revealed interesting EV secretion patterns that differed according to cell line. We demonstrated the presence of EV-DNA and cfDNA in all the cell lines, with varying concentrations. We also found that a common BC mutation in TP53 can be specifically detected in both EV-DNA and cfDNA of cancer cell cultures using droplet digital PCR. The proteomic characterization of EVs through high throughput mass spectrometry revealed common EV signatures and proteins involved in cancer processes and organotropism unique to distinct site-specific cell lines. Specifically, we found enrichment of integrin receptors in metastatic cancer EVs compared to EVs secreted from normal epithelial cells and matched tumorigenic nonmetastatic cell lines. Gene ontology (GO) pathway analysis revealed that cancer derived EVs display a cell adhesion signature and are enriched with proteins involved in extracellular matrix interaction, focal adhesion, endocytosis, and PI3K-Akt signaling pathway. Interestingly, EVs containing heat shock proteins and DNA binding proteins are released by both cancer and normal cells. A total of 460 proteins were quantified with a high confidence level, including 70% of the TOP 200 exosome markers archived by Vesiclepedia. Taken together, we characterized the quantity and cargo of EVs in a unique model of BC organotropism, suggesting that EV-DNA and EVs were informative of normal and cancer states. This work could help to identify BC biomarkers associated with site-specific metastasis as well as new therapeutic targets.