Background: The present study aims to summarise the accessory muscles of the anterior thoracic wall and axilla that can be encountered during breast and axillary surgery and record their incidence and clinical significance. Moreover, the laterality of the atypical muscles is highlighted and possible gender dimorphism is referred. Accessory anterior thoracic wall muscles include: Langer's axillary arch, sternalis muscle, chondrocoracoideus, chondroepitrochlearis, chondrofascialis, pectoralis minimus, pectoralis quartus and pectoralis intermedius.
Materials and methods: The anatomical, surgical and radiological literaturę has been reviewed and an anatomical study on 48 Greek adult cadavers was performed.
Results: Literature review revealed the existence of accessory muscles of the anterior thoracic wall and axilla that have a significant incidence that can be considered high and may, therefore, have clinical significance. For the most common of these muscles, which are axillary arch (Langer's) and sternalis muscle, the cadaveric incidence is 10.30% and 7.67%, respectively. In the current cadaveric study, accessory thoracic wall muscles were identified in two cadavers; namely a bilateral sternalis muscle (incidence 2.08%) extending both to the anterior and posterior surface of the sternum and a left-sided chondrocoracoideus muscle (of Wood) (incidence 2.08%).
Conclusions: Despite the fact that accessory anterior thoracic wall and axillary muscles are considered to be rare, it is evident that the incidence of at least some of them is high enough to encounter them in clinical practice. Thus, clinicians' awareness of these anatomical structures is advisable.
Keywords: accessory muscle; axillary arch; chondrocoracoideus; chondroepitrochlearis; chondrofascialis; pectoralis intermedius; pectoralis minimus; pectoralis quartus; sternalis; variation.