A hard lump inside the breast may be caused by breast tuberculosis, breast hyperplasia and breast fibroma. 1. Breast tuberculosis: Breast tuberculosis is mainly caused by the invasion of breast tissue by Mycobacterium tuberculosis, which is a hard lump at the beginning, and then gradually develops into several hard lumps, which usually do not feel pain when pressed and are connected to the skin. 2. Breast Hyperplasia: Breast Hyperplasia is usually related to the change of hormone level in women’s body, the main symptom is that the breast tissue will appear hard lumps, and there will be symptoms such as chest distension and pain, usually the symptoms will be more obvious before menstruation, and it will be relieved after menstruation is over. 3. Breast fibroma: hard lumps inside the breast if the touch is smooth, and can be pushed back and forth, the number of lumps may be more, smaller, may be breast fibroma tumor. Hard lumps inside the breast may also be other reasons, such as breast cancer, etc., it is recommended to actively go to the relevant departments of the regular hospital to find out the specific causes, so that targeted treatment, usually to maintain a good state of mind, regular routine, good for health.