A solid left breast nodule (BI I RADS category 3) is usually indicative of a high likelihood of a benign tumor. The BI I RADS classification of solid breast nodules allows for grading and assessment of the degree of benignity or malignancy of a breast nodule by imaging.A solid breast nodule category 3, is usually a tendency to be a benign nodule, with good nodal mobility, soft texture, clear and smooth borders, slow growth, and the absence of significant calcification and vascular supply. There is no characteristic invasion into the surrounding tissues. Treatment can be decided according to the size of the nodule. If the nodule is less than 1cm, it can be observed first, followed up and reviewed regularly; if the nodule is larger than 1cm, it can be treated by surgical excision if it is too worrying. Solid left breast nodule (BI I RADS category 3), although it indicates a high possibility of benign tumor, there is still a possibility of malignant transformation, it is recommended to go to the hospital and let the doctor guide further treatment.