"Symmastia is defined as a confluence of the breast tissue of both breasts across the midline anterior to the sternum. It can be surgically corrected by a plastic surgeon.[1]
Symmastia can either be a congenital anomaly or iatrogenic.[2] Congenital symmastia is a rare condition with few published cases. Iatrogenic symmastia may occur following breast augmentation, forming what is also colloquially referred to as a "uniboob""
"Missing cleavage a sign of symmastia
Symmastia is a condition where breast augmentation patients experience a “joining” of the two breasts. This is also known as “bread loafing.”
This condition is where the connective tissue between the two breast, or in the cleavage down the sternum, becomes torn and the skin pulls away from the sternum forming a continuous single breast across the chest. The most common cause of symmastia is the result of an improper placement of the breast implant.
In a typical breast augmentation, the plastic surgeon creates a pocket inside the breast to place the breast implant. If they position the pocket too close to the midline of the chest, this can tear or weaken the integrity of the tissue at the sternum. The tissue may tear and create a continuous pocket across the chest which will require breast implant revision surgery to fix.
Signs of symmastia include:
Noticable “bread loafing” at the sternum
Swelling in the midline
Skin lifting up at the sternum"