Patients with very hard breasts may be caused by milk blockage, breast fibroadenoma and breast cancer. 1. Mammary hyperplasia: Mammary hyperplasia, also known as mammary gland adenopathy, is a common benign breast lesion, which is mainly manifested as breast pain, breast nodule or lump, nipple overflow and other symptoms, so the hardness of the patient’s breasts may be caused by mammary hyperplasia. 2. Breast fibroma: Breast fibroma is a common benign tumor of breast, which is mainly caused by proliferation of epithelial and fibrous tissues of breast, and patients may have single or multiple lumps in breast, which are easy to push, and also lead to hardness of breast, and if it involves the peripheral nerves, it will cause pressure pain and other symptoms. 3. Breast cancer: Breast cancer is a malignant tumor formed by uncontrolled proliferation of epithelial tissues in the ducts or lobules of the breast, which is usually seen in women, and male breast cancer is relatively rare, and early manifestations include breast lumps, nipple and areola changes, and so on, therefore, the hardness of breasts may also be caused by breast cancer. It is suggested that patients should seek medical examination in time, and carry out targeted treatment after clarifying the cause of the disease, and pay attention to monitoring the condition in their life, and have regular checkups.