Painful pressure on the underside of the armpit and the outer side of the breast is more likely to be caused by breast enlargement, which may also appear as a nodule or mass in the breast gland on examination. The patient may also experience regular pain, especially during the premenstrual period. Because the occurrence of breast hyperplasia is regulated by the hormone levels in the body, especially high levels of estrogen and progesterone, it will manifest as obvious swelling and pain, and even accompanied by insomnia and excessive sweating, etc. Ultrasound examination can further confirm the diagnosis. The occurrence of breast enlargement is also related to unreasonable living habits in daily life, so you should pay attention to the regulation of daily life and pay attention to prevention. Physical exercise and local physiotherapy can be carried out appropriately, which can also alleviate the patient’s discomfort. In severe cases of mammary gland hyperplasia with significant pain, which affects the patient’s daily life and work, partial excision of the mammary gland can also be considered as an option.