It is best not to examine the breast during menstruation. Breast diseases have special characteristics and the time of examination is significantly related to the menstrual cycle. During different periods of the menstrual cycle, the mammary glands undergo physiological changes of hyperplasia and rejuvenation under the influence of various related endocrine hormones. Before menstruation, the estrogen level is higher, the glandular tissue of the breast proliferates more obviously, the breast tissue appears to be congested and edematous to varying degrees, the whole breast will be thicker, and some examinations are inappropriate and will affect the judgment of the nature of breast lumps. The most suitable time for breast examination is the 5th-10th day after menstruation, because at this time estrogen has the least influence on breast tissue, breast tissue is in a relatively static state, and abnormalities and lesions in the breast are most easily detected.