The Sternalis Muscle—Incidental Finding of a Rare Chest Wall Muscle Variant During Keloid Excision-Chest Wall Reconstruction

Introduction: The sternalis is a rare (strap-like) parasternal muscle that is well known to anatomists, but relatively unknown to clinicians, including surgeons. Familiarity with the muscle is important in avoiding potential confusion when incidentally encountered. When available, the muscle can be harvested for reconstruction of the chest wall or of nearby region. Presentation of Case: The patient is a 55-year-old man with significant sternal keloids secondary to a previous history of severe acne. The patient desires removal of the keloids. Hence, a decision was made to excise the keloids, followed by immediate reconstruction with a propeller flap. Intraoperative excision of the keloids and undermining of adjacent subcutaneous tissue revealed chest muscle fibers fitting the description of the sternalis muscle. The patient tolerated the procedure without any complications. Discussion: The sternalis muscle can be confused for a mass on mammography, but confusion is resolved by computed tomography/magnetic resonance imaging. It has unclear embryonic origin—perhaps a remnant of the panniculus carnosus and/or derivative of a primitive ventral-longitudinal muscle sheet that give rise to the sternocleidomastoid and the rectus abdominis muscles. It is uni- or bilateral and has 1 or 2 bellies. It originates in the intraclavicular region and inserts onto the rectus sheath, costal cartilages, lower ribs, or external oblique aponeurosis. Conclusion: Not enough is known about the sternalis muscle to draw any conclusion about its utility in reconstructive surgery. It is hoped that cases will be presented in the foreseeable future describing its usage in reconstruction of the neck, chest, abdomen, and perhaps even other places.