Tail-end troubles: imaging of soft-tissue buttock tumours.

Primary soft-tissue buttock tumours are relatively common entities, although they are infrequently reported in the literature. The buttock can be a difficult anatomical site to treat soft-tissue tumours due to the proximity of the sciatic nerve and the propensity of tumours at this site to extend into the pelvis and perineum. Therefore, the radiologist plays an important role in the multidisciplinary assessment of these lesions. Cross-sectional imaging, principally magnetic resonance imaging, is used to determine the exact location and extension of the tumour. Furthermore, certain tumours have characteristic imaging appearances that can help to establish a suitably ordered differential diagnosis. From our prospectively maintained database at The Royal Marsden Hospital, including 225 cases that were treated at the Sarcoma Unit over a 30 year period, we present examples of benign and malignant primary soft-tissue buttock tumours and describe the pertinent imaging characteristics, with emphasis on computed tomography and magnetic resonance imaging findings.