Bilateral breast cysts are benign lesions of female breasts, 7mm cysts are small in size, and their causes are not completely clear, which are mainly related to high estrogen level, abnormal structure of breast ducts and breast hyperplasia. 1. Excessive estrogen level: due to dietary and physiological factors, estrogen level in the patient’s body can rise, which can cause abnormal proliferation of epithelial and mesenchymal tissues in the ducts, and then form breast cysts. 2. Structural abnormality of breast ducts: If the congenital development of breast ducts is abnormal or the structure of ducts is abnormal due to trauma, it can lead to breast secretion not being able to be discharged and then accumulating to form cysts. 3. Mammary hyperplasia: Mammary hyperplasia not only has endocrine disorders, but also leads to degeneration or hyperplasia of breast ducts and lobules, resulting in the formation of cysts. Bilateral breast cysts should also be considered for other reasons, such as cumulus cysts, and it is recommended that the patient go to the hospital, complete the auxiliary examinations to clarify the condition, and then be treated by a professional physician for the condition.