Bilateral Presence of the Musculus Sternalis: An Uncommon Muscular Variant Discovered on Anterior Chest Wall Dissection

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 281–292

DOI: 10.46882/2026/IJAP/000191

Article Type: Case Report

Title: Bilateral Presence of the Musculus Sternalis: An Uncommon Muscular Variant Discovered on Anterior Chest Wall Dissection

Names of Authors: Arthur J. Pendelton¹, Beatrice C. Vance²

Authors’ Affiliations: ¹Department of Anatomical Sciences, University of Manchester, Manchester, United Kingdom; ²Department of Plastic and Reconstructive Surgery, Manchester Royal Infirmary, Manchester, United Kingdom

Abstract:
The musculus sternalis is a rare anatomical variant of the anterior chest wall muscle layer, often misidentified as a malignant mass on routine screening mammograms or chest computed tomography scans. During a standard academic dissection of an 82-year-old female cadaver, a rare case of a well-developed, bilateral musculus sternalis was identified. The muscles were located superficial to the fascia of the pectoralis major muscle, running parallel to the lateral margins of the sternum. On the right side, the muscle bundle measured 12.4 cm in length and 1.8 cm in width, originating from the sheath of the rectus abdominis muscle and inserting into the sternal angle near the sternocleidomastoid tendon. On the left side, the muscle was slightly smaller, measuring 10.8 cm by 1.4 cm, with similar attachments. Both variant muscle strips were innervated by branches of the anterior thoracic nerves (medial and lateral pectoral nerves), suggesting a developmental embryological origin linked to the pectoral muscle mass. No other muscular anomalies were observed in the specimen. This case report highlights a classic anatomical trap for radiologists and surgeons, noting that awareness of this variant prevents false-positive tumor diagnoses and assists in muscle flap designs during reconstructive breast surgery.

Keywords: Sternalis Muscle, Pectoralis Major, Anatomical Variant, Mammography, Chest Wall Anatomy

Manuscript Timeline: Received: July 25, 2026; Revised: August 31, 2026; Accepted: September 14, 2026; Published: September 30, 2026

Citation: Pendelton J.A., & Vance B.C. (2026). Bilateral Presence of the Musculus Sternalis: An Uncommon Muscular Variant Discovered on Anterior Chest Wall Dissection. International Journal of Anatomy and Physiology, 15(9), 281–292. DOI: 10.46882/2026/IJAP/000191

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