Mammography (mammography) is the most basic ancillary examination of the breast and the gold standard for breast screening. Based on the density difference between the lesion and the normal breast tissue, breast cancer can be seen as nodular masses and calcified foci on X-ray. Calcifications in the shape of sand, worms or clusters are characteristic of early stage breast cancer and are useful for early detection of breast cancer. The new generation of digital mammography provides clearer images and more reliable results, and can detect microscopic lesions ≤1.0 cm and some occult lesions with a sensitivity of 85-90% and reduced radiation dose. However, mammography is not foolproof, and some breast cancers do not show up on mammography. Advantages Mammography is simple, convenient and highly sensitive, and is one of the most basic methods for diagnosing breast cancer. Disadvantages Although the radiation dose is greatly reduced, there are still X-ray effects after all. Mammography is not recommended for women under 35 years of age who are not at high risk of breast cancer and do not suspect breast cancer. In particular, mammography should not be done for those under 30 years of age who have not had any children. Mammography has high resolution for calcified shadows, but low resolution for dense or intraductal lesions. It is prone to false positives for small p-dense breast development or combined mastopexy.