Sternalis Muscle in Living Individuals Identified with Computed Tomography

Introduction: The sternalis muscle is a rare muscular variation of the anterior thoracic wall. When present, it can confuse the radiologists as a breast mass on mammograms and pose as a challenge and opportunity at the same time for surgeons during mastectomies or breast augmentation procedures. This study aims to investigate the frequency and anatomy of the sternalis muscle on a large Turkish sample. Material and Methods: Following ethical approval, the presence and anatomy of the sternalis muscle was investigated on thoracic computed tomography (CT) scans of 8408 patients. Results: The sternalis muscle was present in 263 (3.1%) patients. The presence of the muscle was unilateral on the right side in 104 (39.5%), unilateral on the left side in 96 (36.5%), and bilateral in 63 (24%) patients. In 326 hemithoraces, Type 1, Type 2, and Type 3 sternalis muscles were observed in 79.2%, 14.4%, and 6.4% of the patients, respectively. Discussion and Conclusion: The frequency of the sternalis muscle among the Turkish population was relatively lower compared to the previous studies on different ethnicities. In addition, CT provides a detailed evaluation of the muscle.