There is a soft lump under the skin on the side of the nipple, considering that it may be caused by mastitis, lipoma, sebaceous cysts, it is recommended to go to the hospital in time for a detailed examination, and then according to the doctor’s recommendations for treatment. 1. Mastitis: Bacterial infection or poor diet may cause inflammation in the mammary glands, resulting in inflammatory lumps, which may be red, hot or painful. 2. Lipoma: Lipoma is a benign neoplastic lesion caused by the proliferation of adipose tissue. Generally speaking, if it is small in size and does not cause any effect, it can be left untreated, and if it is large in size, it can be treated with surgery to remove it. 3. Sebaceous cysts: palpable subcutaneous mass, mostly round, hard or elastic, normal skin color, smooth surface, no sense of fluctuation, the surface is often adherent to the skin, but the base can be movable; the center of the cyst is often a black pinpoint-sized depression, pressing can overflow white contents, sometimes accompanied by a bad smell. Surgical excision is recommended. In addition, other causes such as breast tumor should also be considered. It is recommended that people with the above conditions should seek medical treatment as soon as possible to find out the causes and then follow the doctor’s instructions for treatment. Normally, we should pay more attention to the reasonable diet, less spicy and stimulating food, and develop good living and eating habits.