Pain in one side of the breast and shoulder is more likely to be caused by mastocytosis. Patients with mastocytosis who have recurrent episodes that do not improve may experience breast tenderness and pain that radiates to the scapular area and axillary area on the affected side, which is also referred to as referred pain and is associated with overgrowth of the breast. Some patients may even experience numbness in the upper extremities, which is a reaction to the enlargement of axillary lymph due to hyperplasia, as well as significant insomnia or palpitations. There are many triggering factors for pain or hyperplasia, including personal psychological factors and external environmental factors. The menstrual cycle also has a significant impact on pain, especially in the premenstrual period when the pain is aggravated, and after the period the symptoms can gradually improve and disappear. Patients with breast hyperplasia should have regular color ultrasound examinations of the breast.