Stabbing pain under the breast can be caused by a variety of reasons, as follows: 1, breast hyperplasia: this condition is the most common, the pain mostly intensifies before menstruation, after menstruation to reduce or disappear; 2, breast malignant tumor: when the breast malignant tumor erosion of peripheral nerves can trigger stabbing pain; 3, fasciitis near the rib cage: patients do not have lumps in the breast, but have deep rib pressure pain, consider fasciitis caused by; 4, breast herpes zoster: patients stabbing pain is obvious, accompanied by skin herpes. Therefore, the occurrence of stabbing pain under the breast requires regular mammograms at the hospital to clarify the cause of stabbing pain under the breast, followed by active treatment.