The sudden onset of needle-like pain in the breasts during the reproductive age should be considered as cystic hyperplasia of the breast, which is a common type of benign breast disease, mainly related to endocrine hormonal changes that cause breast hyperplasia and insufficiency of replenishment. The clinical manifestations are mainly breast pain and hyperplastic nodules that change with the menstrual cycle, and the pain is mostly stabbing or swelling pain, mostly in bilateral breasts, but also in unilateral breasts. If there is a sudden onset of pinprick-like pain in the breast during breastfeeding, the main diagnosis is acute mastitis, which is usually combined with blockage of the milk ducts and milk stagnation, manifested as redness and swelling of the breast with stabbing pain or swelling, and fluctuating lumps can be palpated in the breast when the infection is extensive, and pus-like fluid can be seen overflowing from the nipple. Therefore, when there is a sudden pinprick-like pain in the breast, breast ultrasound should be performed in a timely manner to identify the cause of the pain and actively treat it, and do not take medication blindly to avoid aggravation.