Pain under the breast when pressed is associated with breast cysts, mastitis, intercostal neuritis, and breast tumors. Endocrine disorders in the body can lead to epithelial hyperplasia of the ducts, coupled with increased cellularity, folding and necrosis in the ducts due to ischemia, thus forming cysts. Breast cysts change with the menstrual cycle, and when the hormone level increases before menstruation, the cysts gradually increase in size and become painful when pressed by hand. Acute mastitis can be considered as a result of 1-2 months after the birth of a baby, the excessive discharge of breast milk leads to bacterial invasion, resulting in acute inflammation of the breast and the formation of local lumps, which can cause pain when pressed by hand, and chest pain can be considered as a result of intercostal neuritis, which can form after local cold or trauma, and can be innervated by the 3rd-4th cervical nerves, which can cause chest pain when the nerves are violated. Pain in the breast area is considered to be caused by breast tumor. In the middle and late stage, the tumor grows faster and local pain will occur when pressing the breast.