On examination in the outpatient clinic a 10 × 7 cm firm, fixed lump was found in the left iliac fossa area of the abdomen. Urgent colonoscopic examination revealed mild sigmoid diverticular disease with no evidence of colonic malignancy. Computer Tomography was preformed (Figure (Figure1)1) and showed the mass to be arising from the anterior abdominal wall muscles, in particular the internal oblique and transversus abdominis. There was no evidence of distant metastatic disease to the liver or lungs. The clinical suspicion was of a malignant abdominal wall sarcoma. Fine needle aspiration or percutaneous biopsy was not performed. En-bloc surgical resection of the tumour was performed via a left flank incision (Figure (Figure2).2). At surgical resection the tumour mass involved the internal oblique, transversus abdominis and there was a small area of peritoneal ulceration. No distant disease was found at surgery. The tumour was excised en-bloc with a surrounding margin of healthy tissue (Figure (Figure2).2). Part of the external oblique aponeurosis was preserved to allow adequate closure. The large abdominal wall defect was closed using a sheet of Permacol^® mesh (Tissue Science Laboratories plc, Hampshire, England). The Permacol^® mesh was sutured to the posterior leaf of the rectus sheath medially and the internal oblique laterally using a slow absorbing polydioxanone suture. The remaining external oblique muscle was closed over the mesh and the subcutaneous tissue and skin were closed in a standard fashion.

The surgical specimen measured 11 × 7 × 4 cm. In the centre of the specimen, there was a 4 cm whitish solid tumour. The tumour consisted of relatively large cells with granular eosinophilic cytoplasm and small pleomorphic nuclei with occasional nucleoli (Figure (Figure3).3). No conspicuous mitotic activity was noted. The tumour was completely resected within generous margins of normal tissue. The tumour cells showed strong positive reaction with S100 (Figure (Figure3)3) and were negative with GFAP. The appearances were therefore consistent with a GCT.

The histopathological differential diagnosis can include rhabdomyoma (contains cross-striations and glycogen); hibernoma and fibroxanthoma (contain lipid droplets); and reactive changes with surgical trauma (associated with inflammatory elements and areas of necrosis). A common site for a rhabdomyoma is the heart, which is helpful in the differential diagnosis. GCTs can also be mistaken for squamous cell carcinoma due to marked acanthosis and pseudoepitheliomatous hyperplasia. Immunohistochemistry is essential for the correct diagnosis [7]. Most GCTs stain positive for S100, neuron-specific enolase, NK1-C3 and CD68. They stain negative for epithelial, endothelial and smooth muscle markers.

Patients with completely resected benign lesions are usually cured. Excluding malignant tumours, recurrence is rare (it is more common if complete surgical excision is not achieved). Therefore the prognosis for these tumours appears to be favourable. There is no role for adjuvant therapy with radiotherapy or chemotherapy.

Malignant GCTs are encountered in only 2% of cases [8]. Only around 80 cases have been reported worldwide. They are characterised by necrosis, spindling, vesicular nuclei with prominent nucleoli, increased mitotic activity (> 2 mitoses/10 high power fields), a high nuclear to cytoplasmic ratio and pleomorphism. More than 3 of these features are required for a diagnosis of malignancy. Less than 3 of these features would classify the tumour as an atypical GCT. The prognosis of malignant GCT is poor with risk of local recurrence and distant metastases to lung, liver and bone. Interestingly, four of the reported seven GCTs of the abdominal wall have had malignant features. Our case showed the typical histopathological features of a GCT with no suspicious features of malignancy. However, given the high percentage of malignant lesions reported to be arising from the abdominal wall careful histopathological examination of this anatomical site is recommended.

Extensive abdominal wall defects like the one encountered here are a surgical challenge [9]. The options for surgical closure included: primary closure, the use of prosthetic mesh material and advanced plastic surgical techniques [10]. Primary closure has a high risk of future incisional hernia formation. Plastic surgical techniques (such as pedicled or free myocutaneous flaps from various sites including the rectus abdominis, latissumus dorsi or gracilis muscles) require advanced plastic surgical training and expertise.