The fascial structure of the breast: New findings on the anatomy of the inframammary fold

The inframammary fold defines the shape and structure of the breast, especially in women. As the inframammary fold is placed between the fifth and sixth ribs, the ligaments or fascia are thought to attach from these ribs. However, the previous literature on what structures constitute the inframammary fold does not provide sufficient knowledge for reconstructing the natural form of the fold. This study aimed to clarify the structure that involves the inframammary fold. Ten sides of five formalin-fixed, adult Asian cadaveric breasts were studied. Upon dissection of the breast, including the ribs, the fat lobules were removed while preserving the septal structures under the microscope. The fascial structures were observed grossly and radiographically. A multilayered fascial structure was noted from the dermis near the inframammary fold, anchored to the deep fascia of the pectoralis major muscle mainly at the height of the fourth rib and partially of the fifth rib, from the outside of the nipple to the linea axillaris media, where the fold could be clearly observed. Additionally, the fat lobules around the inframammary fold were subdivided by thin septa closer to the dermis, and they fused posteriorly and upward to form this fascial structure. The inframammary fold was not formed by an adhesion directly under the sixth rib, but by the skin “hanging” from the height of the fourth and fifth ribs due to the multilayered fascial structure that repeatedly fused and dissociated and the changes in the size of the fat lobules. This new anatomical finding may help in inframammary fold reconstruction.