If you can feel a hard lump in the breast lying down, it may be breast hyperplasia, benign or malignant tumor of the breast and so on. 1. Breast hyperplasia is the most common benign breast disease, most common in women aged 30 to 50 years old, mainly manifested as breast pain, nodules or lumps, so lying down can feel the hard lumps, some patients will be combined with nipple discharge. 2. Benign tumors of the breast include intraductal papilloma, breast fibroadenoma, mammary gland adenoma and so on, the common one is mammary fibroadenoma, which is often manifested as smooth, painless lump with clear boundary, and can be touched as hard lumps, and it is common among women aged 20 to 25 years old, and a minority of patients can have different degrees of swelling and pain, hidden pain and dull pain during menstrual cycle. 3. Malignant tumors of the breast, such as breast cancer, are the most common, most of them do not have breast pain, but hard lumps can be felt, the boundary of the hard lumps is not clear, the shape is irregular, and some of them are accompanied by the orange peel sign and the dimple sign of the skin, and the axillary lymph nodes are enlarged. If you feel a hard lump in the breast, you need to go to a regular hospital for examination, such as breast ultrasound, etc., to clarify the cause of the disease and carry out the appropriate treatment.