A right breast hypoechoic nodule is a nodule that is less echogenic than fatty tissue, and a BI-RADS category 4A refers to a low malignant potential with a malignancy rate of 2-10%. A breast nodule is usually a breast mass detected by palpation or imaging such as ultrasound. A right breast hypoechoic nodule is a nodule found on ultrasound on the right side of the breast that is less echogenic than the surrounding breast fat tissue. Hypoechoic nodules are the imaging manifestation of most breast diseases and may be caused by benign diseases such as complex cysts and fibroids, or malignant tumors such as breast cancer. The BI-RADS (Breast Imaging Reporting and Data System) classification is a benign-malignant risk assessment of breast nodules based on imaging findings, and category 4A is defined as a low malignant potential with a 2-10% risk of malignancy. Therefore, a category 4A right breast hypoechoic nodule has a 2 to 10% chance of being the result of a malignant tumor such as breast cancer, or it may be the result of a benign condition such as a breast fibroid. Generally, category 4A breast nodules require histologic examination by puncture or excisional biopsy to further define the nature of the nodule. Patients are advised to consult a specialist for further examination or treatment as prescribed by the doctor, taking into account the shape and size of the nodule.