Adolescent girls with hard lumps on one side of their breasts may have physiological lumps from normal development; they may also have acute mastitis, cystic hyperplasia of the breast, fibroadenoma of the breast, breast cancer, and trauma. 1. Physiological lumps, most commonly seen during puberty, estrogen levels increase, appearing breast hard lump-like changes, as a normal physiological phenomenon, do not require special treatment. 2. Acute mastitis, most common in breastfeeding women, is an acute purulent infection of the breast tissue, early only breast swelling and pain and the formation of hard lumps in the breast, accompanied by local skin temperature increases. 3.. Cystic hyperplasia of the mammary glands, which occurs in women of childbearing age, is characterized by periodic pain in the breasts with the formation of hyperplastic nodules. The degree of pain and the size of the nodules change with the menstrual cycle, i.e., it is aggravated during menstruation and relieved after menstruation. 4. Breast fibroma, which is more common in young people, manifests as a lump in the breast and can be painful. On examination, the surface of the lesion is smooth, with clear boundaries and good mobility. 5. Breast cancer, with no obvious characteristic manifestation in early stage, in advanced stage, irregular shape, hardness and poor mobility lumps can be touched in the breast, accompanied by orange peel sign or dimple sign. 6. Traumatic lumps: the lumps formed after the breasts are hit are often caused by local bleeding, in the early stage of the injury, the local capillaries rupture and bleed, and the bleeding accumulates under the skin to form hard lumps. If there is a hard lump on one side of the chest, it is recommended to consult the hospital for standardized examination and treatment.