A left breast hypoechoic nodule is an ultrasound finding of a left breast nodule that is less echogenic than the surrounding fatty tissue, category 4A is low suspicion of malignancy, and the malignancy rate is between 2 and 10%. Breast nodules are most often detected by palpation or imaging tests such as ultrasound. A hyperechoic left breast nodule is a breast nodule found by ultrasound to be less echogenic than the surrounding subcutaneous fat tissue. Most breast nodules appear hypoechoic. Hypoechoic nodules may be the result of benign conditions such as complex cysts and fibrous tumors, or malignant tumors such as breast cancer. The BI-RADS classification is an assessment of the risk of malignancy of breast nodules based on ultrasound, molybdenum imaging, etc. Category 4A is defined as low suspicion of malignancy, with a malignancy rate of 2-10%, i.e., there is a 2-10% probability that it is due to a malignant tumor such as breast cancer. It is generally recommended that category 4A hypoechoic breast nodules undergo puncture biopsy to further define the benign or malignant nature of the nodule. Patients are advised to consult a specialist for further examination and treatment as prescribed by the doctor.