Breast enlargement is generally referred to as mammary hyperplasia, and the patient’s armpit pain is associated with breast pain radiating to the armpit area. It is also considered to be related to axillary lymphadenitis, mastitis, and breast fibroadenoma. 1. Normal disease response: Usually, breast hyperplasia will cause patients to experience breast pain, breast lumps, nipple discharge and other symptoms. When the pain symptoms radiate to the armpit area, it can be manifested as axillary pain. 2. Axillary lymphadenitis: when there are viral infections in the armpit area, such as hemolytic streptococcus, staphylococcus aureus, etc., the patient may show local lymph node enlargement, pain and other discomforts. 3. Mastitis: When mastitis occurs in patients with breast hyperplasia, it may manifest as breast pain, redness and swelling of the breast, and the pain may also radiate to the armpit area, thus inducing armpit pain. 4. Breast fibroadenoma: the cause is still unclear, and it is considered to be related to female endocrine disorders and gene mutation of breast fibroblasts. Typical symptoms of patients include breast lumps, pain, etc., which can also be manifested as armpit pain. Breast hyperplasia armpit pain may also be caused by malignant tumors. For those whose pain is clearly caused by breast hyperplasia, it can be relieved by local hot compresses. If there are other diseases, you need to follow the doctor’s instructions to use medication to relieve.