Rectus sternalis-a rare anatomical variation found during mastectomy: report of two cases and literature review.

Background: Rectus sternalis (RS) is a rare normal variant of the anterior chest wall musculature; in humans, it is occasionally found while it is part of some animals' musculature. It was first reported in 1604, but it did not catch much attention and was only formally described in 1726. Many names have been used to refer to it, such as RS or musculus sternalis. It is mostly observed in Asians, and in Saudi Arabia, the prevalence was found to be 4%. It can be confused with tumors of the anterior chest wall during routine mammography. Also, it can affect the radiation field after surgery and can be utilized in reconstructive surgery. So, we believe that it is important for oncology surgeons, radiologists, radiation oncologists and reconstructive surgeons to have the knowledge of this rare anatomical variation. Case Description: We report two cases of RS muscle discovered in Saudi Arabian females during modified radical mastectomy for breast cancer, paying special attention to its correct identification, its clinical importance, and its impact on treatment of breast cancer. The first case is a 47-year-old female with bilateral RS who underwent mastectomy for inflammatory breast cancer, while the second is a 50-year-old female with a unilateral muscle who underwent mastectomy for invasive ductal carcinoma. Conclusions: Surgeons should be knowledgeable of such variation as the muscle can be a differential diagnosis, may affect the management of breast cancer, and can be used in reconstructive surgery.