The woman was diagnosed with a fibroadenoma in her breast after being pregnant for more than four months. The 30-year-old woman was torn between the need to cut it and the fear of affecting the health of her baby, and the fear of hormonal stimulation during pregnancy, which could turn into cancer. Breast fibroadenoma during pregnancy is a benign disease with a very low chance of malignant transformation. Considering the physiological characteristics of pregnant mothers, patients need to have a comprehensive clinical and imaging examination as soon as possible. The need for surgical treatment depends on each mother-to-be’s age, physical condition, and the characteristics of the mass itself. Fibroadenoma of the breast, grows fast during pregnancy Fibroadenoma of the breast is usually an isolated breast nodule of one to two centimeters in size, which can often be found during breast self-examination and is usually a painless, smooth, tough and well-mobile mass. As one of the common benign breast lesions in young women, the incidence of breast fibroadenoma is about 7% to 13%, and most of them will accompany women through their youth and shrink until after menopause. The chance of breast fibroadenoma becoming cancerous is very low, and it is generally believed that the chance of fibroadenoma becoming malignant is less than 0.1%. Among the tens of thousands of cases of breast fibroadenoma removed in Tianjin Cancer Hospital, only 4 cases of malignant transformation were found. For young women under 35 years old, asymptomatic fibroadenoma of breast not more than 1 cm in size does not require treatment, and only regular follow-up is needed every 6 months. Breast fibroadenomas are stimulated by estrogen and progesterone to increase in size, and are also affected by lactogen. In the absence of pregnancy, estrogen and progesterone fluctuate periodically at a relatively stable level as the woman’s menstrual cycle changes. When pregnant, estrogen, progesterone and lactogen are all significantly higher than when a woman is not pregnant, stimulating not only the rapid enlargement of breast fibroids, but also causing dramatic changes in normal breast tissue, with rapid increases in volume and density. The longer the pregnancy, the more pronounced these changes become, making detection of breast disease more difficult. We advocate that every pregnant woman should have a comprehensive breast examination before these changes occur, at the first maternity visit in early pregnancy. A breast screening is also necessary before planning a pregnancy, and once a breast fibroadenoma is detected, it can be removed with minimally invasive surgery and then prepared for pregnancy after a good recovery. Breast ultrasound has the least impact on the fetus If a new breast lump is found during pregnancy or an existing breast lump is rapidly increasing in size, a timely visit to a breast specialist should be made. Ultrasound is the first choice for mothers-to-be, as it is a non-invasive, radiation-free examination with high safety and sensitivity, and can identify whether the mass is a fluid-filled structure or a substantial lump, and can help identify breast fibroadenomas, other benign breast lesions and malignant breast lesions. Puncture biopsy is currently the preferred method for histologic diagnosis of substantial masses. If a new mass develops during pregnancy and ultrasound suggests a solid mass, a hollow needle aspiration biopsy needs to be considered. “Current studies point to the safety of performing a puncture biopsy in the first 6 months of pregnancy.” If a breast mass is found late in pregnancy, in the seventh to ninth months of pregnancy, it can be removed after delivery when the ultrasound suggests benign. However, he stressed that mothers-to-be over 35 years old need to be alert once breast fibroids are detected and the possibility of malignant breast tumors should be carefully ruled out. Biopsy required if lump does not disappear after breastfeeding If a clinical diagnosis of breast fibroadenoma is made, the treatment plan should be considered based on the patient’s physical condition, pregnancy week, whether the tumor has rapidly increased in size, pain, milk secretion and other factors. “Surgical excision is not always the preferred approach for patients in pregnancy.” He noted that for masses that have been confirmed benign on biopsy, surgical resection should be delayed until the end of pregnancy or breastfeeding, or until the risk to the fetus and mother is minimal. Masses that can be confirmed benign on biopsy still need to receive close observation and follow-up during pregnancy. This is because significant changes can be found in the breast during pregnancy, with a marked increase in volume or nodularity that may mask abnormal lesions. In addition, because fibroadenomas are stimulated to grow by estrogen and progesterone and lactogen, most fibroadenomas will decrease in size after breastfeeding, and some may even shrink and disappear completely. If the lump does not disappear after breastfeeding, an excisional biopsy may be necessary. Surgical excision should also be considered when the clinical presentation, imaging findings and puncture results are inconsistent. For example, if the ultrasound indicates a benign mass and the mass grows rapidly, then removal of the mass is both confirmatory and curative. The surgery should not be postponed until late in pregnancy Surgery during pregnancy often worries mothers-to-be, believing that it will endanger the health of the fetus. “In fact, in order to minimize the impact of surgery on the fetus, only local anesthesia can be used and fetal monitoring can be performed if necessary.” In general, surgical treatment is not recommended for those with pre-eclampsia, and the stimulation of surgical pain during the procedure may lead to the onset of miscarriage. Surgical treatment is also not recommended during the last 3 months of pregnancy, when blood flow to the enlarged glands is abundant and the ductal system is maturing in preparation for breastfeeding, and after 32 weeks of gestation, the mature ducts begin to secrete milk, at which time complications such as bleeding, infection, and breast fistula are likely to occur if surgical treatment is performed. If the patient’s condition really cannot be delayed and surgery is needed, the first 6 months of pregnancy is a more appropriate time for surgery, provided that contraindications to surgery, such as local anesthetic allergy and pre-eclampsia, are excluded. He emphasized that the need for surgical treatment depends on each mother-to-be’s age, physical condition, and the characteristics of the mass itself, and requires a comprehensive evaluation by a breast specialist to provide the most appropriate individualized treatment and follow-up plan.