Pectoralis quartus: a case report

Abstract

The pectoral muscles come from the same muscular mass. In normal anatomy there are two pectoral muscles: the pectoralis major and the pectoralis minor. It’s prevalent in 11-16% of individuals. The presence of axilary variant muscles may cause neurovascular compression and, in addition, complicate surgical procedures. During regular dissection class, the presence of an uncommon variant in a male cadaver was found: a fourth pectoral muscle with its origins in the costocondral junction of fifth and sixth ribs and insertion at the pectoralis major fascia. It was located inferiorly to the pectoralis minor and posteriorly and inferiorly of the edge of the pectoralis major muscle, further detached from it. We believe that the knowledge of these anatomic variations is significant in some surgical procedures, such as lymphadenectomy. Moreover, knowledge of these variants is also important during imaging procedures, as to avoid misdiagnosis.