Updated project metadata. Using LC-MS/MS, we analyzed ECM-enriched samples obtained from 1) human triple-negative breast cancer samples and matched adjacent normal mammary gland tissues, and 2) disease-free omentum from patient with non-metastatic ovarian cancer and high-grade- serous-ovarian- cancer-derived omental metastasis samples. We conducted the LC-MS/MS analysis on peptides obtained after solubilizing ECM-enriched samples using different methods (crude ECM extract, urea-soluble extract, urea-insoluble extract) and submitted to basic-reversed- phase separation or not.