Sternalis muscle: Importance of its awareness in chest imaging and clinical significance

Abstract

The sternalis is an uncommon, variant muscle of the anterior thoracic wall that is estimated to be present in 8% of the human population. Students in a medical gross anatomy course were fortunate to discover a right, unilateral sternalis muscle during dissection of a 76‐year‐old female Caucasian cadaver. The sternalis appeared as a ribbon‐like strap and measured 15 cm in length with an average width of 2.5 cm. It was oriented on the anterior thoracic wall along the right margin of the sternum and medial to the sternocostal head of the right pectoralis major muscle. Despite its rarity, radiologists must be aware of the possibility of encountering the sternalis during thoracic imaging (CT scans, mammography, MRI) because of the risk for its misdiagnosis as a tumor. Further, risk for surgical complications such as damage to this muscle during breast surgery must be considered. Thus, although it may be difficult to perform a proper anatomic analysis of the infrequently observed sternalis muscle, it is important that students and clinicians be aware of its existence because of its potentially significant impact on clinical diagnosis and patient management. Therefore, anatomic studies through prosections, illustrations, photographs, diagnostic images, and detailed descriptions are warranted to increase awareness of the sternalis muscle and its variations among clinicians (especially radiologists and surgeons).