Scar tissue in the breast is caused by a surgical procedure, such as a breast augmentation, lumpectomy, or mastectomy. Radiation therapy can also cause scar tissue, also known as fibrous tissue. Scar tissue is the result of the body activating its healing process after a cut, injury, or damage has occurred to the skin or cells. The body begins to produce collagen, which forms connective tissue that causes the skin to heal back together. Scar tissue in the breast can cause pain because the connective, fibrous tissues create a tightness or hardness in the breast.

During a breast augmentation procedure, incisions are made beneath the breast or around the areolas so that the surgeon can insert the implants through these incisions. Then the tissues inside the breast are cut to form a place for the implant. The implant may also be placed under the breast muscle. A person's body naturally forms a layer of scar tissue around the breast implant, and scars usually form where the initial incisions were made.

The most common complication associated with breast augmentation is a condition that causes the scar tissue in the breast to tighten or harden around the implant. This condition, known as capsular contracture, can cause pain, discomfort, and deformation of the implant. Capsular contracture occurs in around 20 percent of patients who have undergone a breast augmentation, but it is less common in women who choose to have the implant placed beneath the breast muscle.

A lumpectomy is a procedure in which breast tissue that surrounds a cancerous tumor is removed. The tumor and an additional margin are removed so that the physician can biopsy the tissue to learn if the cancer has spread throughout the breast from the location of the tumor. When the tissue is removed, fluid will infiltrate the space where the tumor was located. Scar tissue will begin to form in this area and will replace the fluid.

Depending on the type of mastectomy performed, the breast tissue, areola, and lymph nodes will be removed. Many women choose to have a breast reconstruction procedure performed at the same time as the mastectomy. Scar tissue in the breast will form after the reconstruction procedure, creating the outer lining around the implant.

Radiation therapy for breast cancer will cause the blood vessels and tissue of the breast to be damaged. The tissue will begin to heal and scarring, also known as radiation fibrosis, will form within the breast. Breast tissue can harden because of the scarring, but physician-prescribed exercises and massages can help to prevent some toughening of the tissue. Women should consult a physician about the risks associated with surgical procedures and the possibility of scar tissue in the breast forming.