Pressing pain on the outside of the breast may be breast hyperplasia, mastitis, trauma, chest muscle pain, chest wall disease, etc. 1. Mammary gland hyperplasia, most of them have obvious cycle, the pain will be aggravated before menstruation, grumpy, often angry, excessive pressure is also easy to trigger. 2. Mastitis, if you are currently breastfeeding, localized pain on pressure and hard lumps on touch, you need to consider the accumulation of breast milk, or acute lactation mastitis. It can also be seen in plasma cell mastitis and breast tuberculosis during non-lactation period. 3. trauma, localized by extrusion, impact and other traumatic injuries may also appear pain, or even swelling, subcutaneous bruising and so on. 4. Chest muscle pain, if lifting things or strenuous exercise before, it may cause chest muscle strain, strain injury, also will appear on the outside of the breast pressure pain. 5. Diseases of the chest wall, such as soft tissue injury of the chest wall, rib fracture, intercostal neuralgia, etc., can also cause pain on the outside of the breast. The pain of pressing on the outer side of the breast should also be considered as malignant tumors, such as breast cancer, and should go to the hospital in time to find out the cause of the disease and then treat it.