In addition to identifying a pectoralis quartus muscle variation, an additional variation of the anterior thoracic wall that has not been reported in the literature was found in a 60-year-old male cadaver. The accessory muscle originated from the aponeurosis of the external abdominal oblique and inserted on the fascia overlying the coracobrachialis muscle. Additionally, the co-existence of an accessory muscle and pectoralis quartus has not been previously described. The current findings and the clinical significance are discussed as a single muscle variation and as two muscle variations in combination.
