The causes of hard lumps in the chest that hurt when pressed include inflammation of the mammary glands, breast hyperplasia, inflammatory breast cancer, and so on. 1. Inflammation of the mammary gland: When the milk in the breast is not discharged in time, it will lead to the accumulation of milk, which will make the mammary ducts blocked, thus forming a hard lump, triggering mastitis or causing abscess. There is localized redness, swelling and pain. 2. Mammary hyperplasia: hard lumps may appear in the breasts, which are painful when touched, and the pain is mainly more intense when menstruation is approaching, and will be gradually relieved after menstruation. It may be accompanied by abnormal nipple discharge. 3. Inflammatory breast cancer: acute inflammation with redness and swelling of breast skin, accompanied by diffuse enlargement of breast nodes and obvious pressure pain. 4. Others: for example, tuberculous protrusion of chest wall, intercostal nerve sheath tumor, excessive bony hyperplasia, etc., all of which can lead to the appearance of hard lumps in the chest and pain when pressed. When there is a hard lump in the chest that hurts when pressed, go to the hospital as soon as possible, to clarify the cause of the disease, to facilitate targeted treatment, so as not to delay the condition.