The formation of breast epidermoid cysts is divided into congenital developmental abnormality and acquired sex, congenital and embryonic developmental abnormality, while acquired sex is mainly related to breast trauma, hair follicle injury and sebaceous cyst rupture. 1. Formation causes: the more common factors are divided into two, one is caused by abnormal development during the embryonic development stage; the other is due to damage to the hair follicles and skin on the surface of the breast, hair and epidermal tissue implanted inside the wound, and then form cysts. In addition, sebaceous cysts can also be formed when they rupture on their own. 2. Symptoms: most of them are painless superficial swellings, hard to touch, round or oval in shape, with a slow growth rate. 3. Treatment: for small size, no obvious discomfort breast epidermoid cysts, do not need to be treated; for large size or pain and other discomfort symptoms, can consider complete excision, infection formed abscess can be incised drainage treatment. It is recommended to go to the hospital to complete the auxiliary examination in order to clarify the condition, and then the professional physician will give the appropriate treatment for the condition.