Application of CfDNA Methylation Detection in Auxiliary Diagnosis of Breast Cancer

This study is investigating whether a blood test that detects cancer-related DNA changes (called cell-free DNA methylation) can help diagnose breast cancer at an earlier stage. **You may be eligible if...** - You have a confirmed diagnosis of breast cancer with known molecular subtype information - You are able to give informed consent - OR you are a healthy volunteer able to give informed consent **You may NOT be eligible if...** - You have had another type of cancer previously or currently - You are pregnant or planning to become pregnant - You have received any cancer treatment (surgery, chemotherapy, radiation, targeted therapy, or immunotherapy) before the blood draw - You have had a blood transfusion in the past month Talk to your doctor to see if this trial is right for you.