Additionally, the protein products of 5 upregulated DEGs (LAMB4, COL9A2, FREM2, and COL10A1) and 12 downregulated DEGs (e.g., COL17A1, COL7A1, and LAMA5) were specifically located in the ECM, indicating that DCIS might be diagnosed via the detection of specific protein factors in blood (Table 3). This evidence concerns the gene COL9A2 and ductal breast carcinoma in situ.