Giant desmoid tumour of abdominal wall: resection and reconstruction by posterior component separation

Abstract

Management of large abdominal wall desmoid tumours is complicated due to the unpredictable behaviour of desmoids and the need for laborious reconstruction of the abdominal wall after wide local excision. A multidisciplinary team approach, including surgeons, oncologists and plastic surgeons, is necessary for proper management. This case highlights the diagnostic and surgical challenges related to the reconstruction of abdominal wall defect, after radical excision of a 30×30×25 cm desmoid tumour, originating from left rectus muscle. The defect was closed successfully by a perspicuous technique of posterior component separation. The awareness of this straightforward technique will allow the surgeons to do these radical procedures with confidence and without any consternation of complex reconstructive procedures.

Background

There has been a paradigm shift in the management of desmoid tumours, from surgical to medical, in recent times. This is based on some large studies demonstrating a similar outcome with wait and watch policy or with chemotherapy.^{1 2} However, this wait and watch policy is recommended for a subgroup of patients with less aggressive behaviour. Desmoids with aggressive growth pattern, worsening symptoms and poor response to the antiestrogen treatment would require wide local excision with a negative margin, for optimal management.³ However, the incidence of recurrence after excision is reported to be high. The size of the recurrent tumour can be larger than the primary tumour, and the rate of relapse is as high as 60%.⁴ The relapse is more common in a younger age group due to aggressive tumour biology or if resection margin is positive or in tumours of larger size.^{3 4} Due to the infiltrative nature of the desmoid, achieving the negative margins usually requires extensive resection. Few articles condemn aggressive resection to achieve the negative margin, as the microscopic negative margin has failed to demonstrate any benefit to decrease the relapse rate. However, this finding has been challenged by many studies.² Given controversy regarding the margin status, it is wiser to achieve the negative margin without compounding the morbidity. The management of abdominal wall defect after excision of the tumour is the most difficult part of the management in large abdominal desmoids. The surgical complexity amplifies with the increase in size of the tumour. These defects are usually managed by a multidisciplinary team. Various reconstructive approaches ranging from biological mesh to flaps are utilised to cover the defect. We explored the possibility of a posterior component separation to close the large defect and were successful. This technique, although requires expertise, is easily reproducible, exploitable and provides excellent functional and cosmetic outcome.

Case presentation

A 38-year-old woman presented with painless swelling over the abdomen for the past 1 year. The swelling was initially noticed in the left upper abdomen. To start with, the swelling progressed slowly over the first 10 months, followed by the exponential increase in size in the last 2 months. She did not have any associated complaints apart from occasional belching and abdominal discomfort. Her menstrual cycles were regular, and she has two children. She underwent bilateral tubal ligation 3 years before. There were no other comorbidities. The physical examination revealed bilateral pitting oedema; the rest of the general examination was normal. The abdomen was hugely distended along with overlying engorged vessels (figure 1). However, the distension was asymmetric, the left side being more protuberant. A non-tender lump was palpable in the abdomen. The lump was approximately 30×30 cm in size, occupying the whole of the abdomen, extending from the xiphisternum to the pubic symphysis and encroaching both the flanks. The surface of the lump was bosselated, and its consistency variegated being soft at places and firm at others. The margins were well defined, except superiorly where the margin appeared to be merging with the costal cartilage. The lump was not palpable on digital rectal examination. The examination of the other systems was normal.

Figure 1.

Abdominal mass with overlying engorged vessels.

Investigations

The routine blood tests were normal. With a provisional diagnosis of liposarcoma arising from the retroperitoneum, involving the abdominal muscle and compression of inferior vena cava, a CT scan was performed. The contrast-enhanced CT of thorax and abdomen revealed well-defined soft tissue mass of size 28×27×22 cm, with few areas of internal necrosis. The mass seemed to be arising from the anterior abdominal wall. The fat plane was maintained with the aorta; however, the infrarenal part of inferior vena cava was not visualised (figure 2). The main arterial supply of the mass was observed to be arising from the left inferior and superior epigastric arteries. Mild mesenteric fat stranding was also noted. To confirm the origin of the mass and involvement of the abdominal muscles, MRI was done, which showed a T2 hyperintense mass of size 28 cm craniocaudally, 27 cm transversely and 22.4 cm antero-posteriorly, which was occupying nearly the entire abdomen (figure 3). The mass was abutting the abdominal wall, and there was thinning of muscles of the epigastric region. Posteriorly, the lesion was abutting the right psoas muscle without any evidence of invasion. The small and large bowel loops were displaced to the periphery. The lesion was also abutting the inferior aspect of the liver. The fat planes with aorta were well maintained, but the part of the inferior vena cava was not seen. A core needle biopsy demonstrated spindle cells within a collagenous stroma without any evidence of nuclear atypia or mitosis.

Figure 2.

CECT abdomen.CECT, contrast-enhanced CT.

Figure 3.

MRI abdomen.

Differential diagnosis

Although the clinical diagnosis was liposarcoma arising from the retroperitoneum, the CT and MRI findings suggested the diagnosis of desmoid tumour arising from the left rectus muscle. The diagnosis was confirmed by the histopathological finding, which demonstrated spindle-shaped cells separated by an abundant collagenous matrix. The cause of pedal oedema could be explained by the compression of the IVC by the desmoid tumour.

Treatment

In view of the compressive symptoms (IVC compression), the tumour board decided for the upfront surgery for the desmoid tumour. An elliptical incision, encompassing the tumour was made. Intraoperatively, a large encapsulated extraperitoneal tumour of size 30×30 cm was seen. It was originating from the left rectus muscle and was extremely vascular with multiple dilated vessels over the attached peritoneum and tumour surface (figure 4). These vessels were secured carefully with sutures and Ligasure@. The lump was resected with a 2 cm clear margin. The majority of the muscles of the left side of the abdomen, including complete rectus muscle, medial 1/3rd of left external, internal and transversus abdominis, were removed with the tumour, leaving a large defect nearly 12 cm in the transverse axis. We were then caught in a dilemma of how best to reconstruct the abdominal wall and close a defect of about 12 cm. Our secondary aim was prevention of the incisional hernia. A posterior component separation technique was finally resorted to after several careful considerations (figure 5). An incision was made over the right posterior rectus sheath about 5 mm lateral to the medial edge of the rectus muscle. The incision was extended superiorly and inferiorly to expose the retro-rectus space. Dissection was continued to the lateral edge of the rectus muscle till linea semilunaris was identified. Further, the dissection was advanced cephalad towards the subxiphoid area and inferiorly towards the space of Retzius. We then crossed to the left retro-rectus space inferiorly. However, since most of the left rectus muscle and medial one-third of obliques and transversus abdominis was removed with the tumour, pretransversalis space was encountered on the left side. The transversus abdominis muscle was exposed by incising the posterior lamina of the internal oblique aponeurosis. The pretransversalis space was developed on the right side by separating the transversus abdominis muscle from the underlying transversalis fascia. The dissection was continued laterally towards the psoas muscle in pretransversalis space. Caudally Cooper’s ligament and pubic bone were exposed bilaterally. Similarly, B/L pretransversalis space was joined cranially along the xiphoid process. The mobilised posterior rectus sheath was closed in the midline by 2–0 polydioxanone (PDS) suture, after removal of the underlying towel. The anterior sheath was closed by running 2–0 PDS after placement of 16F closed suction drain. An onlay polypropylene mesh of size 30×30 cm was secured by interrupted sutures to prevent an incisional hernia (figure 5). Due to loss of about one-third muscles of the left side of the abdomen, the mesh could not be placed in retromuscular space, as originally described in the posterior component separation technique. The extra skin was sacrificed, and then the skin was closed with interrupted sutures (figure 6).

Figure 4.

Desmoid originating from the left rectus sheath with dilated vessels over it.

Figure 5.

Closure of the defect by posterior component separation and polypropylene mesh.

Figure 6.

Skin closure by interrupted sutures.

Outcome and follow-up

The postoperative period was uneventful. She was discharged after 5 days. The final histopathological examination revealed fibromatosis of the left rectus muscle. The margins were free from the tumour. She had marginal necrosis of skin around the umbilical area. The necrosed skin including the umbilicus was debrided in subsequent follow-up. The wound was finally closed on postoperative day 20. She is healthy at the end of 9 months without any evidence of recurrence (figure 7).

Figure 7.

Healthy scar at 9 months.

Discussion

Desmoid tumour, also known as aggressive fibromatosis, is a locally invasive tumour, arising mainly from the muscle, fascia and other connective tissues. They can arise at any part of the body. However, the common sites are mesentery, abdominal wall and the limbs.³ This condition is more common in young females at reproductive age, suggesting hormonal influence.⁵ These tumours have no malignant potential but can rapidly grow and can cause local compressive symptoms. The course of desmoid is not predictable. Sometimes, they can progress rapidly, while in other situations, they remain stable for a long time or may regress spontaneously. More than 85% of desmoids are sporadic and associated with somatic CTNNB1 mutations.³ In the remaining 10%–15%, they present as a part of familial adenomatous polyposis (FAP) and Gardner or Turcot syndrome. The germline mutation of APC is found invariably with patients with FAP and these syndromes.^{2 3} The desmoid tumour is broadly classified into abdominal and extra-abdominal types. Abdominal desmoids are further classified into abdominal wall desmoid and mesenteric desmoid. It classically presents as a painless progressive abdominal lump. The extent of the lesion is best assessed by MRI.⁶ MRI can also be used for the follow-up to detect any recurrence. The image-guided core-needle biopsy usually confirms the diagnosis. It is advisable to discuss the management plan in a multidisciplinary team meeting. Few large studies have confirmed the wait and watch policy for these tumours.^{2 3 7} A trial of antiestrogen or chemotherapy may be given for large tumours.2 3 5 8 The surgical treatment can be justified only in patients who are symptomatic or have a poor response to medical therapy.^{2 3 8} The relapse rate is as high as 40%–60% in some studies.³ The risk of relapse is higher with the larger tumour, young age and positive margins.³ A predictive nomogram, developed by Crago et al,⁴ has been devised to predict the relapse rate. Some studies, however, did not find any association of negative margins with the rate of recurrence.² The high local recurrence is proposed due to infiltrative margins. S45F CTNNB1 mutation is another important predictor for local recurrence, but its routine application is still not recommended.⁹ Adjuvant radiotherapy can be used after incomplete excision of the tumour, but its benefit is not conclusively proven.¹⁰ Studies have shown that radiotherapy at a dose of 2 Gy daily for 28 days can provide local control in 77% and a complete response in 17% of the patients.¹¹ Drugs, like non-steroidal anti-inflammatory drugs, anthracycline-based regimens, methotrexate tyrosine kinase inhibitor and antiestrogen, have also shown benefits in many retrospective studies.^{1–3 5} But good quality prospective studies are not available to frame any guidelines. Our multidisciplinary team decided for surgical intervention in this patient, in view of the compressive symptoms by the huge mass, as evident by bilateral pedal oedema and non-visualisation of the part of the IVC. The decision was discussed with the patient. She was advised to continue with regular follow-up and need of radiotherapy and medical treatment in case of the recurrence. The major challenge was the reconstruction of the abdominal wall. The expected midline defect after excision of the tumour, as reviewed from the MRI, was about 15 cm. A posterior component separation using transversus abdominis muscle release (TAR), first described by Novitsky et al, in 2012, for the reconstruction of the abdominal wall, opted.¹² The technique of posterior component separation, widely known as Rives-Stoppa hernia repair, was first described in the early 1970s.^{12 13} A retro-rectus space of 6–8 cm is created on either side of the midline in this procedure. However, since this space is limited by the fusion of the posterior rectus sheath at the lateral border of the rectus muscle, the procedure is ineffective for a defect of more than 10 cm in width.^12–14 The technique of posterior component separation using transversus abdominis muscle release provides significant posterior rectus fascia advancement to cover a defect of as large as 20 cm.^12–14 This advancement and large space for mesh placement are obtained by the division of the posterior rectus fascia, just medial to the linea semilunaris and neurovascular bundle followed by the release of the transversus abdominis muscle from the underlying transversalis fascia and peritoneum along its entire medial edge. A preoperative non-contrast CT scan is handy to decide the type of the procedure based on the defect size and width of the rectus muscle. According to Love et al, TAR will be required in addition to Rives-Stoppa repair, if the width of the defect is more than the sum of the rectus muscle on CT scan.¹⁵ Apart from the component separation, other techniques like synthetic mesh, dual mesh and myo-cutaneous flap were considered. All these techniques have been described earlier with variable success.1 5 8 16 The choice of the procedure should be based on the location of the tumour, size of the defect and expertise of the surgeon. In our opinion, the posterior component separation with TAR is easy to learn, reproducible and can be used to cover a defect size of up to 20 cm. Another advantage of TAR is the placement of large mesh (>1000 cm²) in a well-vascularised area, more economical (avoid dual mesh), preservation of neurovascular bundle, less hernia recurrence and restoration of physiological properties of the repaired abdominal wall.^12–14 Complex reconstructive procedures like myo-cutaneous flap (latissimus dorsi flap, deep inferior epigastric flap and free flap) should be reserved for recurrence and with extensive muscle loss. These flaps are associated with significant morbidity due to the large area of dissection and poor cosmesis. In contrast, TAR has fewer complications due to the preservation of the neurovascular bundle. The cosmesis is also better since it avoids a separate incision; besides, the repair is durable and more physiological. Few authors have used the method of posterior component separation for the abdominal wall reconstruction after desmoid excision.⁸ Addition of the TAR procedure to posterior component separation can be utilised for the closer of larger defects, created by excision of the abdominal wall tumours. With increasing awareness and expertise, we expect wider utilisation of this method for abdominal wall reconstruction after the excision of desmoid. The procedure has the potential to emerge as the procedure of choice for reconstruction of the abdominal wall defect.

Learning points.

• Recent publications support wait and watch policy for desmoid tumours. Hormonal therapy should be considered for all patients as first-line treatment. However, large, symptomatic desmoids, not responding to hormonal treatment, should be treated by surgical excision.

• Preoperative assessment of the tumour with CT helps immensely in assessing the appropriate size, its vascularity and the extent of the muscle involvement.

• The local recurrence rate is as high as 40% after surgical resection. Every attempt should be made to obtain a negative microscopic margin to reduce the recurrence.

• Posterior component separation with transversus abdominins release can cover a midline defect up to 20 cm. The procedure is easy to learn, reproducible and durable and physiological repair of the abdominal wall defect. However, the type of repair should be based on the size and location of the tumour and surgeon expertise.