It is not normal for women to have hard lumps in their breasts. The causes of hard lumps in women’s breasts include breast hyperplasia, mastitis and breast cancer. 1. Breast enlargement: Breast enlargement is a disorder of the mammary gland structure during normal development or degeneration of the mammary gland, which is clinically manifested by breast pain and swelling, nodules or lumps, and some patients may also experience yellowish fluid overflow from the nipple. 2. Mastitis: Mastitis refers to inflammation of the breast tissue with or without infection. Lactating mastitis is acute and often manifests itself as chills and high fever, redness and swelling of the skin, and in severe cases, the lumps will form abscesses or even break out; non-lactating mastitis is a chronic disease that manifests itself as a lump with pain and swelling at the breast accompanied by inverted nipples and fluid overflow. 3. Breast Cancer: Breast cancer is a tumor in which the epithelial tissues of the breast proliferate and go out of control under the action of a variety of cancer-causing factors. Early symptoms of breast cancer are not obvious, often manifested as painless lumps in the breast, nipple overflow, areola abnormality, and so on, and in the late stage, there are symptoms of emaciation, fatigue, fever, and anemia, and so on. Hard lumps in the chest may also be caused by breast fibroma, breast trauma, etc. When patients experience discomfort, they should go to the hospital immediately.