Hard lumps in a girl’s breasts may be related to various diseases such as breast hyperplasia, breast fibroma, breast malignant tumors and so on. 1. Breast Hyperplasia: Breast Hyperplasia is mainly manifested as breast swelling, tingling, and touching will feel obvious irregular hard lumps, which is caused by the proliferation of breast tissue. 2. Breast fibroma: Breast fibroma is clinically manifested as a round or oval lump in the breast, the boundary of the lump is clear, the mobility is generally good, it is a common benign tumor. 3. Breast malignant tumor: Breast malignant tumor is also known as breast cancer, the lump is generally unclear edges, poor mobility, and easy to adhere to the surrounding tissues. Girls with hard lumps in the chest may also be trauma, mastitis and other causes, the normal breast tissue texture is softer, no lumps, hard lumps in the chest recommend that patients go to the hospital as soon as possible to determine the cause of the disease before treatment.