Lead Sponsor

Sun Yat-sen University

Age

18 - 75 years

Sex

ALL

Healthy Volunteers

No

•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.

•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.