Accessory mammary glands, also known as ectopic breast, multiple breast disease, can also be accompanied by multiple nipples. Accessory mammary glands is a kind of common disease, which is a congenital breast dysplasia disease caused by the original breast not degraded or incompletely degraded in the fetal period. Most of the patients often seek treatment because of the appearance or unbearable symptoms. Different treatment options are determined by the different age stages and different positions of the accessory mammary glands. Therefore, this article reviews the mechanism, classification, clinical manifestations, diagnosis and treatment of accessory mammary glands formation in combination with domestic and foreign literature, in order to provide reference for the diagnosis and treatment of accessory mammary glands.