Abrant origion and distribution of pectoral nerves with prominent ansa pectoralis and absent lateral pectoral nerve

During the dissection of the left axilla of an 80-year-old male cadaver three anterior and one medial pectoral nerves were incidentally detected. All the three anterior pectoral nerve arose from the anterior division of the middle trunk of the brachial plexus. The upper two anterior pectoral nerves entered pectoralis major while the most inferior joined the medial pectoral nerve to form a prominent ansa pectoralis. The ansa pectorals then gave four branches that distributed to the two pectoralis muscles. Two of the ansa pectoralis branchesentered pectoralis major, one ended on pectoralis minor and one entered both muscles. No lateral pectoral nerve from the lateral cord was observed. Though the presence of multiple branches like in this case would make approach to the pectoral region difficult without damage to these nerves, it could safeguard the normal muscle function in situation of isolated nerve injuries