An unusual variant of an accessory thoracic muscle
, 1, 2, 2, 1, 1, 3, 1
Abstract
Background: The anterior thoracic wall musculature presents significant morphological variability. The current literature describes a few accessory thoracic muscles (ATMs) and discusses possible clinical implications. The dissection report describes an unusual ATM variant.
Materials and methods: The variant case was identified during the routine dissection of a 78-year-old female donated cadaver.
Results: An accessory previously unknown muscle was identified on the right anterior thoracic wall in the intermediate plane of the pectoralis major and minor muscles (PM and Pm). It originated from the external oblique muscle (at the level of the fifth rib), and in its distal attachment, the muscular belly became aponeurotic and fused with the axillary fascia. The insertion was located anteriorly to the axillary neurovascular structures but was not closely related. On the left anterior thoracic wall, the musculature was presented as typical.
Conclusions: The variant case could not be classified as a previously reported variant due to its origin in the external oblique muscle. The proposed name for the accessory muscle is the “abdomino-fascialis” muscle. Surgeons operating in the axilla and the anterior thoracic wall must acknowledge these variants, which can significantly complicate several procedures.
Keywords: accessory thoracic musclevariationdissectionanatomy
References
- Asghar A, Naaz S, Narayan RK, et al. The prevalence and distribution of sternalis muscle: a meta-analysis of published literature of the last two hundred years. Anat Sci Int. 2022; 97(1): 110–123.
- Carrera A, Chaiyamoon A, Reina F, et al. Pectorobrachioepicondylaris musculoaponeurotic band: case description with evidence of median nerve compression. Anat Cell Biol. 2023; 56(2): 280–284.
- Douvetzemis S, Natsis K, Piagkou M, et al. Accessory muscles of the anterior thoracic wall and axilla. Cadaveric, surgical and radiological incidence and clinical significance during breast and axillary surgery. Folia Morphol. 2019; 78(3): 606–616.
- Kim PW. Variations in the anterior thoracic wall with sternalis muscle and accessory pectoralis major muscle. Surg Radiol Anat. 2022; 44(5): 785–790.
- Macalister A. Additional observations on muscular anomalies in human anatomy. (Third series) with a catalogue of the principal muscular variations hitherto published. Trans R Irish Acad. 1875; 25: 1–134.
- Natsis K, Vlasis K, Totlis T, et al. Abnormal muscles that may affect axillary lymphadenectomy: surgical anatomy. Breast Cancer Res Treat. 2010; 120(1): 77–82.
- Palagama SPW, Tedman RA, Barton MJ, et al. Bilateral chondroepitrochlearis muscle: case report, phylogenetic analysis, and clinical significance. Anat Res Int. 2016; 2016: 5402081.
- Taterra D, Henry BM, Zarzecki MP, et al. Prevalence and anatomy of the axillary arch and its implications in surgical practice: A meta-analysis. Surgeon. 2019; 17(1): 43–51.
- Tubbs RS, Shoja MM, Loukas M. Bergman’s comprehensive encyclopedia of human anatomic variation. John Wiley & Sons, Inc., Hoboken 2016.
- Venieratos D, Samolis A, Piagkou M, et al. The chondrocoracoideus muscle: a rare anatomical variant of the pectoral area. Acta Med Acad. 2017; 46(2): 155–161.
- Zielinska N, Karauda P, Węgiel A, et al. A very rare case of a thoracobrachialis muscle. Surg Radiol Anat. 2023; 45(11): 1493–1496.
- Zielinska N, Moryś J, Paulsen F, et al. Morphological variability of the pectoralis major muscle in human fetuses. Ann Anat. 2023; 249: 152108.
- Zielinska N, Pośnik M, Koptas K, et al. Accessory thoracic muscles in human foetuses. Folia Morphol. 2024; 83(3): 700–706.
- Zielinska N, Ruzik K, Georgiev GP, et al. A new variety of chondrocoracoideus muscle, or an additional head of pectoralis major muscle. Surg Radiol Anat. 2022; 44(2): 233–237.
- Zielinska N, Ruzik K, Podgórski M, et al. Morphological variability of the pectoralis major muscle in human fetuses. Ann Anat. 2023; 249: 152108.
