A. Axial contrast-enhanced CT image of the abdomen demonstrates a heterogeneous soft tissue mass in right anterior abdomen extending to the pelvis, approximately 22 x 12 x 25cm in size. The peripheral parts of the mass are solid and hypervascular, as demonstrated by the early enhancement.

B. Axial delayed contrast-enhanced CT image of the abdomen demonstrates progressive contrast enhancement in the periphery of the mass. The central part of the mass is hypoenhancing and may be necrotic or cystic.

C, D. The peripheral enhancing portion of the mass is mildly hypermetabolic, with SUV_max of 2.2, whereas the central portion is hypometabolic.

E. Large hypermetabolic mass is again noted in the right anterior abdomen.

Surgical pathology showed high grade sarcoma with immunohistology stains suggestive of possible pleomorphic liposarcoma. The mass contained large areas of myxoid components, corresponding to the hypoenhancing and hypometabolic central portion of the mass.

As details of the previous radiotherapy sites were not available for this case, it is difficult to determine whether our patient's sarcoma arose secondary to radiation, or whether it was naturally occurring. Post-radiation sarcomas are a recognized, though uncommon, complication of radiotherapy, which is commonly used for treatment of malignant disease. The most common primary diagnoses are breast cancer, lymphoma and head and neck cancer. The most common sarcoma histopathologic subtypes are osteosarcoma, malignant fibrous histiocytoma and liposarcoma. The imaging findings are not pathognomonic, but knowledge of the past history and an appreciation of the expected latency period may help to suggest the diagnosis. Such tumours are often difficult to treat. Differential diagnoses in this case may have included: giant pedunculated hepatic haemangioma; or primary peritoneal gastro-intestinal stromal tumour (GIST), which usually more highly FDG-avid.