Imaging tumours of the retroperitoneum

•. Tumours of the retroperitoneum occur infrequently. They are usually malignant and include primary neoplasms (retroperitoneal sarcomas, extragonadal germ cell tumours, paragangliomas) and lymphomas. Benign retroperitoneal tumours are very rare. •. Except for well differentiated liposarcoma, mature teratoma, lipoma, neurofibroma and lymphangioma, most primary retroperitoneal neoplasms do not have characteristic imaging features. Histology is always needed to confirm the diagnosis. •. Imaging is important in the diagnosis and management of retroperitoneal tumours, to guide biopsy, to identify the tumour boundaries prior to surgery and to screen for metastatic disease. •. Despite surgery, radiotherapy and chemotherapy, the prognosis of patients is generally poor, since malignant retroperitoneal tumours are usually locally advanced or metastatic at the time of diagnosis.