Women normally have only one pair of breasts, but there are women who have breasts and nipples growing on other parts of the body in addition to the pair of breasts on the chest, which are called parametrium. During embryonic development when the fetus is about 9 cm long (corresponding to the sixth week of embryonic development), six to eight pairs of nipple-like local thickening of the epithelial tissue from the ectodermal layer occur on both sides of the fetal abdomen, from the axilla to the inguinal line (usually called the mammary line), which is the starting base of the breast. Normally, when the embryo is in its 9th week of development, all the small protrusions, except for the pair of primordia on the breast, begin to degenerate and disappear completely by the time of birth. If they do not degenerate before birth, multiple nipples or breasts will appear after birth, which is called paramecium. The most common site of multiple breasts or polypastia is in the outer upper part of the normal breast near the axilla, or between the normal breast and the umbilicus. It is usually often overlooked. The parametrium can become swollen and even painful during a woman’s period, pregnancy, or lactation, and sometimes secretes a small amount of milk-like material. This deformity of the breast often has a genetic predisposition. This condition occurs not only in women but sometimes in men as well, but is 4-5 times more common in women than in men. Some parametrial breasts can also develop to a full extent and can be as diseased as the normal breast, but the incidence of parametrial breast cancer is also significantly higher than that of the normal breast and also significantly higher than that of benign parametrial tumors.