Chest center swelling and pain may be caused by trauma, costochondritis, leukemia, pneumothorax, acute mastitis, cystic hyperplasia of the breast and so on. 1. Trauma: The chest will be swollen and painful in the center of the chest because of subcutaneous hematoma on the chest surface and fracture of the sternum after the chest has been violently collided and extruded. 2. Costochondritis: Chest trauma, infection and other factors lead to damage to the rib cartilage at the junction of the sternum and ribs and inflammatory reaction, so the center of the chest is swollen and painful. 3. Leukemia: malignant proliferation of a large number of leukemia cells in the bone marrow cavity of the sternum leads to a significant increase in the pressure in the bone marrow cavity, so the chest center will be distended. 4. Pneumothorax: after the surface of chest wall or lung surface is broken due to trauma, outside gas enters into the pleural cavity, which leads to the increase of pressure in the pleural cavity, so the center of chest will be distended and painful. 5. Acute mastitis: breastfeeding women’s milk secretion is too much to be utilized, leading to the blockage of mammary gland ducts, and the inflammatory lesions of the mammary glands appear after secondary bacterial infection, so the center of the chest is swollen and painful. 6. Breast cystic hyperplasia: cysts are formed after the expansion of breast gland ducts and lobules under the effect of estrogen, resulting in breast lumps and breast swelling and pain. The swelling and pain in the center of the breast may be related to many factors, and it is recommended to consult a doctor for a clear diagnosis.