Photoacoustic (PA) imaging (PAI) emergerd as a rapidly evolving biomedical imaging modality, which combines the merits of optical imaging and ultrasound (US) imaging, and has a capacity in morphological, functional and molecular imaging, showing potential in visualizing superficial organs. The goal of this clinical trial is to build a PAI standardized scoring system to identify benign and malignant tumors, and use PAI to further determine the molecular classification of malignant breast tumors, and monitor the efficacy of neoadjuvant chemotherapy (NAC) in breast cancer. The main questions it aims to answer are:

1. How to build a standardized PA/US scoring system in differential diagnosis of benign and malignant tumors?
2. Can PAI precisely determine the molecular classification of breast tumors?
3. Can PAI systems predict the efficacy of NAC in breast cancer?

Participants will receive regular PA/US imaging examinations during four stages of NAC (before NAC, 2 Cycles, 4 Cycles and 6 Cycles). And the effectiveness of PA/US in predicting NAC for breast cancer at different time points will be evaluated.

The multi-modality PA/US imaging system was built on a high-end commercial US platform and allowed real-time imaging of grey-scale US imaging, Color-Doppler US (CDUS) imaging and dual-wavelength PAI. The PA/US images were acquired using a hand-held probe integrated optical devices and US transducers. Researchers plan to recruit participants planning to undergo breast nodular surgery from the outpatient department of breast surgery in Peking Union Medical College Hospital. The patients are scheduled to receive multi-modality imaging examinations using the novel imaging system. First, conventional US scanning of the breast, including grey-scale US and CDUS, will be carried out by an experienced US operator. Afterwards, PA/US imaging will be implemented for breasts by the same operator. And the conventional ultrasound and photoacoustic information of the tumor will be assessed, including the tumor size, shape, boundary, calcificaition condition, the tumor blood flow and blood oxygenation. This clinical trial aims to address three key objectives: the development of a standardized PAI scoring system for distinguishing benign from malignant tumors, the application of PAI to assess the molecular classification of malignant breast tumors, and the use of PAI to monitor the efficacy of neoadjuvant chemotherapy (NAC) in breast cancer.

Inclusion Criteria:

1. The patients were above 18 years-old;
2. The patients were presented with a breast tumor, which were clearly shown on routine ultrasound; Biopsy or surgery of breast lesions was performed within 1 week and pathological diagnosis was obtained.
3. Patients agreed to participate in this experiment and signed the Subject Informed Consent.

Exclusion Criteria:

1. Pregnant or lactating women;
2. Breast inflammation or local external injury;
3. The breast mass has been excised for biopsy.
4. Poor photoacoustic imaging effect.
5. Deep lesion location (>3.5 cm)