Journal of Surgery

Introduction

Extensive resections of chest wall soft tissue for cancer extirpation, particularly following breast cancer or radiationinduced angiosarcoma, can result in large, complex soft tissue defects that are challenging to reconstruct. Achieving reliable and timely coverage is essential not only for wound healing, but also to avoid delays in post-resection adjuvant therapy, which has been shown to reduce recurrence and mortality [1]. In many cases, reconstruction must be staged, especially when tumor margins are uncertain. However, when oncologic control can be confirmed pre-operatively, a single-stage approach is ideal, allowing patients to recover and proceed with adjuvant treatment more expeditiously. Workhorse pedicled flaps commonly used for chest wall reconstruction include the pectoralis major, latissimus dorsi, and rectus abdominis flaps. While effective in many cases, their size and vascular reliability may be insufficient to provide coverage for larger defects extending towards the clavicle or past the midline [2]. Additionally, free flap reconstruction may not be feasible and has a risk of complete flap failure. An underutilized yet promising alternative is the External Oblique Myocutaneous Flap (EOMCF). With dual blood supply from the deep circumflex iliac artery and segmental intercostal perforators, this Mathes and Nahai type V flap provides a generous surface area coverage (averaging 400 cm² and reaching up to 800 cm² in an obese individual), preserves some cutaneous innervation via the 6^th - 12^th intercostal nerves, allows for harvest without patient repositioning, and typically permits primary donor site closure [3-5]. Despite its anatomical advantages, the use of EOMCF in oncologic chest wall reconstruction is seldom reported in literature. There remains a need to better define its clinical utility, outcomes, and place within the reconstructive algorithm. In this case series, we describe our institutional experience using the external oblique myocutaneous flap for single-stage closure of large chest wall defects following cancer resection. We highlight surgical technique, patient outcomes, and flap feasibility as a reconstructive option for managing extensive chest wall defects.

Materials and Methods

Patients and Study Design

A retrospective review was conducted of patients with advanced or recurrent breast cancer who underwent extensive mastectomy and chest wall reconstruction using an External Oblique Myocutaneous Flap (EOMCF) at Henry Ford Health between September 2014 and September 2024. Extracted data included patient demographics, cancer history, tumor pathology, resection margins, recurrence rates, overall survival, and post-operative complications.

Histopathological Evaluation

Patients with Ductal Carcinoma In Situ (DCIS), Invasive Ductal Carcinoma (IDC), or Invasive Lobular Carcinoma (ILC) underwent preoperative biopsies, which were histologically confirmed by the pathology department prior to surgery and were planned for wide local excision or mastectomy. In cases of Radiation-Induced Angiosarcoma (RIAS), pre-operative punch biopsies were taken 5 cm circumferentially from the visible tumor margins and sent for pathology. Once pathology confirmed absence of malignancy in the punch biopsy samples, surgical oncology proceeded with wide local excision and a single stage reconstruction was performed by plastic surgery using EOMCF

Surgical Technique

All reconstructive surgeries were performed by the senior author. Under general anesthesia, patients were placed in a supine position with both arms abducted at 90 degrees. All patients received prophylactic preoperative antibiotics. Preoperative skin incision lines were marked to delineate the extent of the mastectomy, including the tumor and/or overlying skin, as well as the design for the ipsilateral EOMCF (Figure 1, 2A). Following wide local excision, the ipsilateral EOMCF was harvested. A midline incision was made through the skin and subcutaneous tissue, extending down to the anterior rectus fascia. The caudal border of the flap was designed in a “V” shape to facilitate V-Y primary closure and allow for a greater arc of cephalad rotation (Figure 1, 2A, 2B). The skin flap was elevated from medial to lateral in the subcutaneous plane, sparing the anterior rectus fascia until the semilunar line was identified. At this point, the external oblique aponeurosis was incised longitudinally, and the external oblique muscle was identified and separated from the underlying internal oblique. Dissection continued laterally between the external and internal oblique muscles to the midaxillary line. The external oblique muscle was then divided from its attachments to the anterior iliac crest and costal margin. The deep circumflex iliac artery was ligated and divided. SPY angiography was used to confirm adequate perfusion to the flap. Once sufficient vascular supply was verified, drains were placed beneath the flap, which was then rotated cephalad and inset into the defect. Closure was performed in three layers: Scarpa’s fascia was approximated first, followed by placement of deep dermal sutures, and completed with a subcuticular suture for skin closure (Figure 2C).

Figure 1: Elevation of external oblique to be used as rotational advancement flap (left). Closure of donor site in V-Y fashion to allow further advancement and greatest coverage (right). Illustration by author R.S.M.

Figure 2: [A] External Oblique Myocutaneous Flap (EOMCF) preoperative markings; [B] Chest wall defect (top), intraoperative incision pattern (bottom); [C] V-Y closure.

Results

Over a ten-year period, six women were identified who underwent External Oblique Myocutaneous Flap (EOMCF) reconstruction following breast/chest wall cancer excision. The mean age was 67.2 years (range: 42-89 years), and the mean Body Mass Index (BMI) was 29.0 kg/m² (range: 22.7-34.7 kg/m²). Two patients (33%) were former smokers, while four (66%) had never smoked. Three patients (50%) had hypertension, and two (33%) had comorbidities such as hypercholesterolemia, diabetes, and/or coronary artery disease (Table 1). At the time of reconstruction, three patients carried a diagnosis of radiation-induced angiosarcoma (RIAS) following prior external beam radiation to the chest wall. All patients underwent immediate reconstruction at the time of wide local excision. Individual outcomes are detailed (Table 2). The mean tumor span was 86.75 mm (range: 42-150 mm). Following excision, the average chest wall defect measured 30.83 cm in length (range: 25-40 cm) and 18.33 cm in width (range: 10-25 cm). The mean area of the chest wall skin defect reconstructed with an EOMCF was 575 cm² (range: 250-800 cm²). The average pathologic margin was 16.7 mm (range: 2-35 mm). Mean operative time for flap harvest and inset was 2.6 hours (range 1.6-3.9). Patients required an average of 2.5 drains (range 2-4), which were on average removed during the first or second postoperative visit. There were no cases of complete flap loss, postoperative hematoma, or abdominal wall hernia. All patients healed within an appropriate timeframe. Two patients (33%) experienced partial flap necrosis—one managed surgically with a 12 × 4 cm skin graft, and the other treated conservatively with bedside debridement and local wound care. During follow-up, three patients experienced disease recurrence within five years. There were three total mortalities: two due to metastatic progression, occurring at a mean of 30.5 months postoperatively, and one secondary to chemotherapy-associated leukemia. Three patients are living without evidence of disease recurrence (Table 3).

Table 1: Patient smoking history and comorbidities.

Table 2: Patient demographics, cancer type, tumor and defect characteristics, pathologic margins, and operative times.

Table 3: Patient complications, adjuvant chemotherapy, time to recurrence, disease specific survival*, and 5-year survival. *(>months) means the patient is living at the time this study was completed.