Two months ago, a young mother visited our breast and thyroid department. The patient was 33 years old and complained of a mass in her right breast two years ago when she took a bath. On examination, it was found that in addition to a 7*8cm mass in the upper outer quadrant of the right breast, a 1*0.8cm nodule could also be found under the areola of the left breast, which was considered as a possible bilateral breast malignancy in combination with breast ultrasound, MRI and mammography. The patient was very depressed when she learned that she had bilateral breast cancer. With the communication and encouragement from the doctor in charge, the nurse in charge and the patient’s volunteers, she quickly gained a full understanding of her condition and actively cooperated with the doctor; however, another problem arose: the lumps on both sides of the patient’s breasts were malignant and the sizes were very different, so it was especially important to choose the appropriate treatment plan. Our doctors discussed the case in depth according to the guidelines of breast cancer and finally formulated a treatment plan of neoadjuvant chemotherapy before surgery for her. On the morning of November 29, after 4 courses of neoadjuvant chemotherapy in the central venous port, the patient’s right breast lump shrank significantly, and the decision was made to immediately perform a modified radical surgery for bilateral breast cancer. After the operation, the patient was in a better mental state and her condition was more stable. She is now undergoing post-operative adjuvant chemotherapy in our department and preparing for bilateral breast reconstruction about 2 years after the operation (the patient is young and bilateral, and 1.5 years after the operation is the peak period of breast cancer recurrence and metastasis). According to Lv Gang, director of the Department of Breast and Thyroid Medicine, the breast is a paired organ that is affected by both endocrine and carcinogenic factors, so theoretically, breast cancer can occur in both mammary glands. Although unilateral breast cancer is more common in clinical practice, there are a few people who have bilateral breast cancer, most of them are found to have tumors in the opposite breast during hospitalization, which is commonly referred to as bilateral primary breast cancer. The overall incidence of this type of breast cancer is not high, ranging from 12-21% in Europe and the United States to 0.4-2% in China. In recent years, the detection rate of this disease is significantly higher than before through routine preoperative bilateral breast ultrasound, mammography and/or random biopsy of the contralateral breast. Therefore, for the exact lesion not detected by manual examination, but the microcalcifications seen by imaging should be taken seriously. Bilateral breast cancer is not worse than unilateral breast cancer if diagnosed early. Therefore, women should insist on regular self-examination of their breasts and go to regular hospitals for further examination as soon as abnormalities are detected. In addition, it should be noted that although there is no difference in prognosis between bilateral breast cancer and unilateral breast cancer, there is a higher chance of local recurrence and metastasis, therefore, it is more important to insist on regular review after surgery, usually once every 3-6 months within 5 years after surgery; once a year within 6-10 years.