There is an 18mm nodule in the left breast which is painless and may be breast fibroid or breast cancer. 1. Breast fibroma: It is a common benign breast disease, caused by the abnormal sensitivity of breast fibroblasts to estrogen. It manifests itself as a painless, movable breast lump. It may not recur after surgical removal, and some patients may not need treatment. 2. Breast cancer: a kind of malignant tumor, mostly occurring in middle-aged and old-aged women, with no pain in the early stage, clinically manifested as a hard, non-smooth lump with unclear demarcation from the surrounding tissues, which can be rapidly enlarged in a short period of time, and the skin on the surface of the breast can be changed into an “orange-peel-like” shape, and cancer cells can be seen in the pathology examination by puncture. It is recommended that the patient should consult a doctor in time, and if necessary, choose the pathology examination under the doctor’s guidance to determine what kind of disease it is, and carry out targeted treatment or observation.