The common causes of hard lumps in the breast during puberty are breast hyperplasia or fibroadenoma of the breast, non-lactating mastitis, and breast cancer. 1. During puberty, the endocrine hormone secretion of the female body is more vigorous, especially the gonadal hormones, such as estrogen, which will lead to stimulation of the mammary glands and hyperplasia, the higher the sensitivity to hormone secretion, the mammary glands will be more likely to be stimulated and hyperplasia, and excessive mammary gland hyperplasia will be formed in the breast of the manifestation of the hard lumps. 2. In the period from puberty to middle age, fibroadenoma of the breast is more likely to occur, is a kind of benign tumor, is due to the excessive proliferation of the mammary gland to form a nodule caused by the touch is relatively hard, smooth and can be pushed, as if the texture of the rubber ball. 3. Mastitis is an inflammatory reaction that occurs when the mammary gland is infected by certain bacteria, and is usually characterized by redness, swelling and pain, and there may be hard lumps in the breast. It needs to be differentiated from hard lumps formed by milk stagnation during breastfeeding. 4. Breast cancer can be found as a lump in the breast, and other secondary manifestations such as nipple discharge and breast skin abnormalities may also occur. Breast lumps are hard in texture and have irregular edges. It tends to invade the surrounding tissues, such as pulling on the skin to form a localized depression in the skin, resembling a dimple. Or block the lymphatic vessels leading to lymphedema, showing orange peel-like changes. The presence of hard lumps in the breast during adolescence requires active consultation and rational treatment under the guidance of a physician.