The painful pressure on the breast near the armpit may be due to mastopathy, mastitis, breast cancer and other diseases. The most typical symptoms are breast pain, lumps or breast overflow. Mastitis is mostly caused by bacterial infection, resulting in localized redness and swelling, strong painful pressure, and the need to extract pus from the inflamed area. Patients with breast cancer may have swollen and painful breasts and lumps, especially in the advanced stage when the axillary lymph nodes are enlarged and press on the nerves in the arms, spreading to the armpits and shoulders, which may cause painful pressure. In addition, it may be caused by abnormalities in the axillary lymph nodes or other breast diseases, so it is best to go for further examination in time to avoid missing the best treatment time.