A hard lump in the middle of two breasts may be caused by subcutaneous lipoma, fibroma, sebaceous cysts and other diseases, or it may be caused by breast cancer. 1. Subcutaneous lipoma: it may be caused by excessive obesity or eating a lot of fatty food, which leads to the accumulation of local fat. 2. Fibroma: it is mainly caused by endocrine disorders or family heredity, etc. If it does not get effective treatment in time, it may cause local hard lumps. 3. Sebaceous cysts: if you don’t pay attention to personal hygiene for a long time, the dirt in your body may block the sebaceous ducts, resulting in localized lumps. 4. Breast cancer: hard lumps in the middle of both breasts may also be malignant tumors growing in the breast area, which are usually accompanied by painless hard lumps in the middle of the breasts, changes in the skin of the breasts, nipple overflow, enlarged lymph nodes and other clinical symptoms. Hard lumps in the middle of the breast may also be caused by adenitis and extra-mammary diseases, etc. It is recommended that the patient consult a doctor as soon as possible to clarify the cause of the disease.