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). The gene discussed is FREM2; the disease is ductal breast carcinoma in situ.