Multilocular bone tumour.

A Greek man age 65, right leg amputee, complained of back pain. On examination there was a large mass in the right groin. Investigation Pelvic radiograph and computed tomography. Figure 1 There is a disarticulation amputation at the right hip with a large well defined multilocular defect in the right ilium. Figure 2 A CT section through the sacrum shows a large, well defined expanding mass with a thin well defined high attenuation rim, and a defect in the mid-ilium. The attenuation of the mass is less than muscle. 459 Figure 3 At a more caudal level the mass replaces the anterior part of the ilium leaving only a thin irregular interrupted lateral margin of bone. A thin higher density capsule surrounds the lower attenuation mass. Figure 4 In a section at the level of the lower sacrum the mass is smaller containing small bone fragments. Comment A multilocular bone lesion with well defined margins can be due to a number of diverse conditions including plasmacytoma, metastasis, especially from renal cell carcinoma, hyperparathyroidism forming a 'brown tumour' or 'osteitis fibrosa cystica' as well as the pseudotumour associated with haemophilia and hydatid cysts of bone. Most of the above conditions can be excluded by the history, examination, biochemical tests or sonography. Hydatid disease occurs in Greece and can be confirmed by a complement fixation test as in this case.