Breast cancer is a common malignant tumor among women, and about 1 to 3 percent of breast cancers occur during pregnancy or lactation. Breast cancer during pregnancy and lactation refers to breast cancer that occurs during pregnancy and one year after delivery. During pregnancy and lactation, the hormonal level of women’s body changes, estrogen secretion is strong, breast tissue proliferation and congestion, and immune function decreases, resulting in faster tumor occurrence, and it is not easy to detect early, thus its prognosis is also poor. Some studies have proved that the incidence of tumors in people whose first full-term birth is later than 35 years old is significantly higher than those whose first birth is before 20 years old. The symptoms are mostly painless breast lumps, which are mostly discovered unintentionally by the patient. In a few patients, the first symptom is nipple discharge, nipple erosion or nipple retraction. Small nodular glandular tissues may often be palpated in the breast that has been nursed during palpation. As the lump grows, it may become “dimple-like”, giving the skin an “orange peel” appearance, or “armor-like” after the tumor has extensively infiltrated the skin. If breast cancer is diagnosed during breastfeeding, breastfeeding should be stopped immediately and different treatment options should be used depending on the condition. Breast cancer is a common superficial tumor and early detection and diagnosis is not difficult.