Langer's arch: a rare anomaly affects axillary lymphadenectomy.

Langer's arch is the best-known anatomic variant of definite surgical implication in the region of the axilla. This rare anomaly is a muscular slip extending from the latissimus dorsi (LD) muscle to the tendons, muscles or fasciae around the superior part of the humerus. In this report, we present a rare case of left axillary arch. During modified radical mastectomy for breast cancer, we encountered an abnormal muscle slip crossing the axilla from the LD muscle to the posterior surface of the pectoralis major muscle anterior to the neurovascular structures. Preoperative knowledge is essential to identify such unusual anomaly and avoid potential complications both intra- and postoperatively.