There are many causative factors for breast cancer, such as unreasonable dietary structure, too much animal protein, environmental pollution and stressful work, which may cause the body’s immune system to become dysfunctional and stimulate tumor production. Similarly, during pregnancy and breastfeeding, women enter the high incidence of breast cancer during lactation (pregnancy). It is characterized by high malignancy, rapid progression, recurrence and metastasis, and symptoms similar to inflammation, thus it is very easy to be ignored. On March 29, 2011, a Sudanese patient, Ms. AZIZA, was admitted to the Breast Clinic of Shanghai Red House Hospital, where she found a fingernail-sized lump in her right breast when she gave birth to her fifth child nine months ago. She was diagnosed with lactational mastitis and given anti-infective symptomatic treatment. A few months passed, but the symptoms were not relieved, and the lump gradually increased in size and pain. After a friend introduced her to the Red House Hospital, she came to see the doctor. After careful examination, the doctors found that Ms. AZIZA had a lump of about 20*18 cm in her right breast, with a hard texture and obvious skin adhesions, and several scattered subcutaneous nodules were visible above the right breast, while the skin surface above it was broken and had yellowish-white discharge. After careful discussion, the doctors concluded that breast cancer could not be ruled out, and after consulting the patient, a partial excision biopsy of the right breast mass was performed. As expected, the frozen section showed invasive breast cancer in the right breast. The clinical diagnosis was “breast cancer during lactation”. What is breast cancer during lactation (pregnancy)? Breast cancer during pregnancy is primary breast cancer that occurs at the same time of pregnancy or within one year of pregnancy. And primary breast cancer that occurs during breastfeeding is called breast cancer during lactation. This type of breast cancer is less common clinically, but should not be taken lightly. According to foreign reports, the incidence of breast cancer accounts for about 2-3% of all breast cancer patients, while in China, the incidence is higher than foreign reports, accounting for about 7-12% of all breast cancer patients. The clinical symptoms of breast cancer during lactation are similar to those of breast cancer in general, mainly lumps and nipple drainage in the breast, which is usually a single duct in one breast. It is often accompanied by enlarged axillary lymph nodes. Due to the enlargement of the breast and the increased density of the breast tissue, X-ray examination often does not easily reveal the tumor, making early diagnosis somewhat difficult. Why do you get breast cancer even during pregnancy and breastfeeding? Nowadays, there is a common view that women who do not have children and do not breastfeed have a higher chance of breast cancer. However, what cannot be ignored is that the period when women are pregnant and breastfeeding is the high incidence of breast cancer during breastfeeding (pregnancy). This is because the hormone level in women’s body is greatly changed during pregnancy and breastfeeding, and the secretion of estrogen and progesterone is high, which stimulates the growth of breast cancer. Why is breast cancer during lactation (pregnancy) easily misdiagnosed? Breast cancer during lactation is often diagnosed with delay. Many breast lumps and lactation are considered as normal physiological reactions during pregnancy, so it is not appropriate for both patients and doctors to detect them. At the same time, the enlargement and swelling of the breast can affect the accuracy of visual and palpation, making examination and identification difficult. And the proliferating breast tissue during pregnancy itself will form a high-density background in the X-ray, which is similar to the X-ray presentation of breast cancer and difficult to distinguish. All these hinder the timely diagnosis of breast cancer. Ms. AZIZA, the main character in the above case, was delayed in diagnosis due to these reasons. How to distinguish breast cancer during lactation (pregnancy) from mastitis】 Mastitis during lactation (pregnancy) can be easily confused with mastitis. However, in acute mastitis, the skin redness and swelling can be limited and bright red in color, while in lactating (pregnancy) breast cancer, the skin changes are extensive, often involving the whole breast and dark red or purplish red in color. In acute mastitis, the axillary lymph nodes are relatively soft and do not adhere to the surrounding tissues and are mobile when pushed, while in lactating (gestational) breast cancer, the axillary lymph nodes are enlarged and hard, adhere to the skin and surrounding tissues and are not mobile when pushed by hand. 3. From the point of view of systemic symptoms: Acute mastitis often has chills, high fever and other obvious systemic inflammatory reactions, while breast cancer during lactation (pregnancy) usually has no obvious systemic inflammatory reactions, and if accompanied by fever, it is low fever. 4. From the point of view of disease duration: acute mastitis has a short course and anti-inflammatory treatment is effective, while breast cancer during lactation (pregnancy) has an aggressive condition and anti-inflammatory treatment is ineffective. How to detect breast cancer during lactation (pregnancy) at an early stage】 Abnormal symptoms of breast during pregnancy and lactation should be seen by a doctor immediately. If there is any unnoticeable inflammation or lump, it is better to go to a specialized hospital for consultation and ultrasound examination if necessary. It is important to note that receiving a breast ultrasound will not affect the health of the fetus if you are more than three months pregnant. Early detection and treatment of breast cancer during breastfeeding (pregnancy) is clinically effective. However, the key is whether women themselves can pay attention to self-care.