Implications of Anomalous Pectoralis Muscle in Reconstructive Breast Surgery

The Oblique Pectoralis Anterior

Katherine Marie Huber, BS; Travis Guthrie Boyd, BS; Amy R Quillo, MD; Bradon J Wilhelmi, MD


ePlasty. 2012;12 

In This Article


This 45-year-old patient underwent left mastectomy for breast cancer and immediate reconstruction with tissue expander. At the time of her mastectomy, she was noted to have an extra muscle anterior to her pectoralis major muscle. The fibers of this extra muscle were oriented obliquely and in the perpendicular direction to the underlying pectoralis muscle (see Fig 1). This oblique pectoralis anterior muscle originated from the sternum medially and coursed inferiorly to insert on ribs 5 and 6 and the anterior rectus aponeurosis. The pectoralis major muscle was normally developed underneath this accessory pectorals muscle. During the dissection to create the pocket for the insertion of the expander, the oblique pectoralis anterior muscle was released inferiorly along the same level as the pectoralis major muscle. The subpectoral pocket was created, preserving the pectoralis minor muscle. Specifically, a mentor CPX3 350 cc tall profile expander was used for her expansion. Her expansion course was routine and lasted 4 months until the distance from the clavicle to inframammary fold matched her right breast and chest wall, which was 29 cm. The total amount of left expander fill at this point was 540 cc. (see Fig 2). Moreover, her left mastectomy specimen weight was 535 g. Once this goal measurement of 29 cm was met, we waited 1 more month to minimize contraction at implant exchange. At her expander exchange operation, the expander was deflated and removed through her previous incision. Superior, inferior, and medial capsulectomy was required to adjust her subpectoral pocket to accommodate the 600 cc high-profile mentor memory gel implant. (see Fig 3) No acellular dermal matrix was utilized in this implant procedure.

Figure 1.

This intraoperative photograph of the left breast (a) demonstrates the aberrant pectoralis accessory muscle, the oblique pectoralis anterior, with its fibers perpendicular (b) to the underlying pectorals major muscle.

Figure 2.

This photograph demonstrates the patient after her last expansion prior to the expander to implant exchange. Notice the small bandage over the port.

Figure 3.

This photograph demonstrates the patient after expander to implant exchange. The permanent implant was placed under both the oblique pectoralis anterior and pectoralis major muscles. A 600 cc high-profile mentor memory gel implant was used for her reconstruction.