Giant mixed retroperitoneal sarcoma with metaplastic bone and cartilage formation: Radiological-pathological correlation

Soft tissue sarcomas account for less than 1% of all malignancies and 10% of them arise in the retroperitoneal tissues 1,2 . The prognosis for patients with retroperitoneal sarcoma varies widely but is usually poor, with reported five-year survival rates ranging between 12% and 70% 1-6 . Complete surgical resection is the treatment of choice 7 . An accurate preoperative diagnosis is necessary to enable the most radical surgical excision of the mass. A 53-year-old woman was admitted to our hospital because of a six-month history of a painless but growing palpable mass of hard consistency located in the right upper quadrant of the abdomen. The patient’s medical history was unremarkable except for iron deficiency anemia. Physical examination revealed a solid, palpable mass occupying the right upper abdomen. There was no palpable lymphadenopathy. Plain X-ray of the abdomen showed a vast, ill-marginated calcified radiopacity projecting over the right upper quadrant (Figure 1). Ultrasound examination detected a large multilobated, mixed echogenic mass extending from the right iliac wing to the lower surface of the liver, inseparable from the medial aspect of the ipsilateral kidney, which appeared invaded and displaced medially. Spiral CT of the abdomen revealed a single, large mass characterized by heterogeneous soft-tissue density with some areas of fatty density on non-contrast images. The upper part of the mass was completely calcified and the mass appeared to originate from the retroperitoneal space. After administration of intravenous contrast medium the mass showed heterogeneous enhancement (Figure 2). The patient underwent radical surgical excision of the lesion with resection of the right kidney. Histological examination showed predominant features of myxoid and round cell liposarcoma. These areas were juxtaposed to high-grade leiomyosarcoma cells, with some areas of lipoma-like type; malignant fibrous histiocytoma-like areas with malignant cells arranged in whorls were also detected. Metaplastic bone and cartilage formation was also observed, especially in the upper portion of the mass. The final pathological diagnosis was mixed retroperitoneal sarcoma with metaplastic bone and cartilage formation. The patient is free of disease at one year from diagnosis. Retroperitoneal sarcomas are often very large at diagnosis because they become symptomatic only when they reach the size of a huge mass or when there is as