Breast cancer (BC) is one of the leading causes of death in Canadian women, with an average survival rate of 5 years after diagnosis. Early detection of BC can greatly improve patient outcomes and survival. However, a non-invasive BC detection method is not contemporarily available in clinics. Recent studies suggest that proteins in small extracellular vesicles (sEVs) could be promising biomarkers for non-invasive BC early-stage diagnosis. sEVs are membrane-enclosed vesicles secreted by cells, which drive different stages of carcinogenesis in BC. The purpose of this work is to analyse different published proteomics data in order to identify enzymes that can be potentially used as diagnostic biomarkers for BC. For proteomics analyses, sEVs were derived from different metastatic breast cancer cell lines and a non-cancerous epithelial breast cell line. The results were generated from three proteomics approaches: quantitative proteomics, phosphoproteomics, and protein acetylation analysis. The enzymes with high abundances in cancerous cell lines were extracted from the quantitative proteomic data. Similarly, phosphorylated and acetylated enzymes in the cancer cell lines were extracted. Among these approaches, we proposed a list of enzymes, including their metabolic pathways, that can be explored as potential BC biomarkers. Future validation of enzymes using both cancer cell lines and blood from BC patients remains to be determined.