Breast tissue consists of glandular tissue and fatty tissue. In clinical practice, when performing mammograms, there are often reports indicating dense shadows in the breast tissue, which is normal and not a cause for concern. In young women, there are more glandular tissues and less fatty tissues in the breast, so the mammogram will show dense shadows, while after menopause, fatty tissues will gradually replace the original normal breast glandular tissues. In other words, the dense shadow of mammogram only indicates that there are more components of breast glandular tissue, not breast tumor changes, and has no relationship with the condition of the breast. This is a normal and common mammogram performance for women between the ages of 20 and 40, so regular review is all that is needed.