Miti-gene Recurrence Score in HR+/HER2- Chinese Breast Cancer Patients

Inclusion Criteria: 1. Diagnosed age: 18-75 years. 2. Early-stage invasive breast cancer, pN0-1. 3. Molecular subtype: HR-positive (ER and/or PR positive), HER2-negative. 4. At least five years of follow-up records (including cases with disease progression within five years and documented records). 5. Sufficient FFPE samples for sectioning or frozen samples for RNA extraction and subsequent testing. Exclusion Criteria: 1. FFPE samples with tumor content \<20%, and inability to enrich tumor regions through cutting. 2. Insufficient extracted nucleic acid quantity or severe degradation preventing further experiments. 3. Failure in RT-PCR amplification of housekeeping genes. 4. Multiple primary breast cancers or a history of ipsilateral or contralateral breast cancer. 5. Disease progression unrelated to breast cancer. 6. Lack of prior signed consent for retrospective scientific research or exemption from informed consent.