Recently, the Women and Children Center of Beijing Children's Hospital received a special patient who was 8 weeks pregnant. The pathological examination report indicated that she was diagnosed with breast cancer. With the postponement of modern women's childbearing age, the probability of discovering breast cancer during pregnancy is increasing year by year. Breast cancer during pregnancy refers to primary breast cancer occurring during pregnancy or within one year after delivery, including breast cancer during pregnancy and breast cancer during lactation. Breast cancer during pregnancy and lactation is not uncommon, accounting for about 5% of all breast cancer cases. Why are women prone to misdiagnosis and missed diagnosis during pregnancy and lactation? During pregnancy and lactation, the levels of sex hormones in women's bodies are significantly higher than usual. Under the stimulation of these hormones, the mammary glands may experience hyperplasia and swelling. At this time, many breast lumps and lactation are considered normal physiological reactions during pregnancy, so they are not easily detected. At the same time, the hyperplasia and swelling of the breast will affect the accuracy of visual diagnosis and palpation, and there will be some difficulties in inspection and differentiation, which hinder the timely diagnosis of breast cancer, leading to the misdiagnosis and missed diagnosis of breast cancer in pregnancy. And breast cancer happens to be a tumor that responds to hormones. Therefore, under the stimulation of high estrogen level, breast cancer during pregnancy is more likely to cause metastasis and recurrence of breast cancer than other periods, affecting disease control and treatment effect. To sum up, breast cancer in pregnancy is insidious and develops rapidly, and is often locally advanced when diagnosed. Should women terminate pregnancy if breast cancer is found during pregnancy? The survival of pregnant women with breast cancer does not conflict with their fertility, and the need to terminate pregnancy is related to pregnancy. 1. breast cancer occurs in the first three months of early pregnancy. We recommend stopping pregnancy because chemotherapy has a high risk of teratogenicity. 2. In the middle and late stages of pregnancy, the order of surgery and chemotherapy should be determined based on the size of the tumor, as the fetal development at this stage is relatively mature and less affected by chemotherapy, which can achieve the dual goals of controlling cancer and giving birth to the fetus. In the third trimester of pregnancy, we recommend radiation therapy and endocrine therapy after delivery. Chief Physician Li Yi of the Breast Center reminds female friends that pre pregnancy breast examinations are very important. Women should fully attach importance to self care of their breasts and understand their basic breast condition before preparing for pregnancy, so as to provide reference and control during pregnancy and lactation. During pregnancy and lactation, women should pay more attention to their own breast condition. Once there are no obvious signs of inflammation or abnormal symptoms such as palpation of lumps or nipple bleeding, they should not ignore it. They should seek medical attention from a regular professional hospital in a timely manner, undergo B-ultrasound examination, and if necessary, undergo biopsy of the lumps. It should be pointed out that receiving breast ultrasound during pregnancy does not affect the health of the fetus. Wang Xuenan from the Women and Children's Center of Beijing Children's Hospital