Hidden pain in the upper right part of the left breast may be caused by trauma, breast hyperplasia, breast fibroma, mastitis, breast cancer, chest wall disease and other factors. 1. Trauma: If the upper right part of the left breast is traumatized by impact, knocking, collision and other traumatic injuries, it may lead to vague pain symptoms. When the trauma is severe, severe pain may also occur. 2. Breast hyperplasia: If the patient has a vague pain in the upper right part of the left breast, it may also be caused by breast hyperplasia. Most of them are caused by the disturbance of sex hormones in the patient’s body, such as estrogen and progesterone. 3. Breast fibroma: Breast fibroma is a kind of benign tumor that occurs in the breast tissue, which may cause vague pain in the upper right side of the left breast. 4. Mastitis: Mostly seen in breastfeeding, milk stagnation accompanied by bacterial infection, acute inflammation, redness, swelling, heat and pain, chills and high fever, and sometimes there will be a vague pain in the upper right of the left breast. 5. Breast Cancer: The massive proliferation of breast epithelial cells causes the formation of breast lumps, nipple discharge, breast tenderness and other symptoms; hidden pain in the upper right side of the left breast may occur. 6. Chest wall diseases: such as costochondritis, pleurisy, herpes zoster and other diseases may cause vague pain in the upper right side of the left breast. If you have vague pain in the upper right side of the left breast, you should go to the hospital immediately, and give appropriate treatment and therapy after clarifying the cause of the disease.