After neoadjuvant therapy, the primary lesion in breast cancer patients may experience tumor regression, which increases the difficulty of distinguishing between breast cancer and adjacent tissues. Raman spectroscopy is a form of scattering spectroscopy, which offers rapid and sensitive analysis, delivering detailed biochemical information and molecular signatures of internal molecular components within the sample. This study aims to discern between cancer and adjacent tissues after neoadjuvant therapy in breast cancer patients using label-free Raman spectroscopy.

Inclusion Criteria:

• (1) aged ≥ 18 years; (2) histologically confirmed invasive breast cancer (clinical tumor stage T1 to T4, nodal stage N1-3, and metastasis stage M0); (3) previous treatment with neoadjuvant chemotherapy with or without target therapy (such as trastuzumab, pertuzumab), or endocrine therapy; (4) enough frozen samples of breast cancer tumor and adjacent tissue.

Exclusion Criteria:

• (1) undergoing sentinel lymph node biopsy with indocyanine green dye or methylene blue injection after neoadjuvant therapy; (2) Breast cancer during pregnancy and lactation, inflammatory breast cancer.

patients with local advanced breast cancer who had completed surgery after neoadjuvant therapy from Renji Hospital, School of Medicine, Shanghai Jiao Tong University.