There are many reasons for the growth of buttocks, such as sebaceous cysts, boils, lipomas and so on. 1. Sebaceous cysts: there are more sebaceous glands secreting in the buttocks, if the excretion of sebaceous glands is obstructed, it will cause the phenomenon of buttocks sebaceous cysts, which can be manifested as subcutaneous nodules that rise on the surface of the skin, and some patients are able to see the contents of them from the surface openings. 2. Boils: If the local skin follicles and the deep surrounding tissues of the buttocks are infected by Staphylococcus aureus, it may cause nodules, which may show one or more lumps on the buttocks skin, accompanied by pus or whiteheads on the surface, and usually accompanied by pain. 3. Lipoma: Lipoma may be related to heredity and other factors, which may show palpable nodules on the surface of the buttocks or under the skin, usually not accompanied by other discomforts, and the nodules are more movable and soft in texture. There are many reasons why there is a bag on the buttocks, and after the symptoms appear, you should go to the hospital in time to improve the examination and give standardized treatment after a clear diagnosis, and you should not ignore the symptoms, so as not to delay the diagnosis and treatment of the disease.