Girls have hard lumps in their breasts for a variety of reasons, mainly lobular hyperplasia of the breast, breast fibroma, breast cancer and so on. 1. Lobular hyperplasia of the breast. It is also commonly referred to as cystic hyperplasia of the breast. This is a benign hyperplastic lesion that may be accompanied by breast tenderness and nipple discharge. 2. Breast fibroma. This kind of disease is caused by the overgrowth of breast lobules stimulated by androgens, which is a kind of benign tumor, and most of the patients have no other accompanying symptoms except hard lumps in the breasts. 3. Breast cancer. This is a kind of cell malignant proliferative disease, this kind of patients in addition to breast lumps, there will be nipple overflow, skin cellulite changes, nipple inversion pulling, etc., is a common malignant disease of the breast in middle-aged and elderly women. Hard lumps in the breasts may also have other causes such as mastitis, breast trauma, etc., and should be consulted as soon as possible for a clear diagnosis.