A little pain in the underarms of the breasts may be caused by trauma, mastitis and breast hyperplasia. 1. Trauma: When the patient’s armpit is bumped, the symptoms of a little pain in the armpit will appear, usually no treatment is needed, as long as no strenuous exercise, after a period of time will be restored. 2. Mastitis: Mastitis can be caused by bacterial infection, which can cause symptoms of pain in the breasts, and can be treated with antibiotics under the guidance of a doctor. 3. Mammal hyperplasia: Mammal hyperplasia may be caused by endocrine disorders, endocrine disorders will appear mammary gland hyperplasia, there may be symptoms of paratesticular breast pain, you can under the guidance of the doctor’s advice to take non-steroidal anti-estrogenic medication to carry on the treatment, the common medication is tamoxifen citrate tablets. At the same time, underarm paratits may also be painful when they are subjected to friction, breast cancer, or breast fibroadenoma. It is recommended that patients with underarm paratesticular breasts should consult a regular hospital immediately to clarify the cause of the pain and treat it actively to prevent the possibility of paratesticular breast cancer.