The breast self-examination is an examination of the breasts, performed by a woman, ideally one time per month. The goal of the breast self-examination is for a woman to notice changes in the breast that should be brought to the attention of a physician for further evaluation. These include breast lumps, changes in the breast shape, size, or contour, or skin changes. Randomized trials have shown no decrease in breast cancer mortality among women performing monthly breast self-examination. Despite this, the American Cancer Society recommends monthly breast self-examination for women over the age of twenty.
Thomas, D. B.; Gao, D. L.; Self, S. G. et al. (1997). "Randomized Trial of Self Breast Exam in Shangai: Methodology and Preliminary Results." Journal of the National Cancer Institute 89:355–365.