Growing four breasts is polymastia, which is the presence of two additional secondary breasts in addition to the normal 1 pair of breasts, usually located in the upper outer part of the normal breasts. Polydactyly is a congenital developmental abnormality of the breast. Fetal breast primordia can develop into breasts under normal circumstances, the excess breast primordia will degenerate and disappear before birth, and some of those that do not degenerate, in addition to the normal breasts, the excess breasts will develop to form the secondary breasts, which leads to polydactyly. The secondary breasts are usually found in the chest and are often located in the upper outer part of the normal breasts, i.e., in the armpit area. Depending on the degree of development of the secondary breasts, they can also be categorized as fully developed or incompletely developed. The secondary breasts may also suffer from breast cancer. If the secondary breasts are too large in size and affect your life or if the secondary breasts have pain, discomfort or lumps, it is recommended that you seek medical attention in time for treatment.