Once received a pregnant woman in pregnancy, 29 weeks gestation, left breast mass 4 * 3 size, ultrasound suggests: left breast mass, solid occupancy, surrounding see obvious blood flow signal. Admission biopsy: suggestive of invasive breast cancer. For breast cancer in pregnancy, clinicians are prone to neglect, often the rapid development of the disease, the lump is large, is considered to be the development of the breast during pregnancy and hyperplasia, ignoring the condition. The patient was kept in labor until 37 weeks after surgery, and a healthy baby girl was delivered by cesarean section, followed by conventional chemotherapy and radiotherapy. The patient is now 2 years postoperative and in stable condition. Breast cancer in pregnancy should not be ignored and should be taken seriously by pregnant women. Although the malignant degree is high, the treatment is positive and timely, and the curative effect is still certain.