What should I do if I find a lump on my breast? The most important thing is to clarify the nature of the lump by means of some tests. Pathological results obtained through lump biopsy are the most effective way to develop a treatment plan. Compared to surgical biopsy, puncture biopsy causes less damage to normal tissue, no scarring, and the patient only needs local anesthesia, which is easily tolerated. However, will puncture biopsy cause breast cancer metastasis? Many patients may have this question. The fact is that various stimuli to the tumor, including general mechanical compression and surgery, may cause tumor cells to be shed and enter the blood circulation, but this does not necessarily lead to metastasis because the body’s immune system will quickly kill them. It has been found that the metastasis of breast cancer is still mainly related to the factors of tumor and the internal environment of the body itself. A large number of data confirm that there is no difference in the outcome of breast cancer patients who underwent puncture biopsy and those who underwent direct surgery without puncture. A large number of follow-up studies of breast cancer patients who have undergone puncture biopsy with hollow core needles for up to 15 years have found that surgical treatment within 2 weeks after puncture biopsy does not decrease the survival rate of patients. There is also no evidence to confirm that postponing surgery for 1 month after puncture biopsy is detrimental to patients. Therefore, puncture biopsy of the breast is a safe and reliable diagnostic method and patients do not need to worry about it causing metastasis of cancer. Once the puncture biopsy is confirmed to be cancer, patients should actively cooperate with doctors for timely and regular treatment.