Teaching Case

Three weeks later her paresthesia had progressed to the gluteal and genital regions with development of urinary and faecal incontinence. CT of the pelvis revealed an enhancing lobulated sacral tumour with fluid levels compressing the sacral spinal canal and extending into the right greater sciatic notch, with an enlarged IVC containing peripherally enhancing thrombus (Fig. 2). MRI confirmed the sacral mass containing fluid levels and loss of the sacral canal (Fig. 3). MR angiography and venography confirmed the slightly enhancing tumour thrombus within the IVC (Fig. 4).

Review of the original venogram showed right sacral bone destruction (Fig. 1). Subsequent CT of the thorax demonstrated multiple pulmonary metastases (Fig. 5).

Sacral surgical biopsy showed multinucleate giant cells with no aggressive features, confirming the diagnosis of giant cell tumour (osteoclastoma). In the presence of IVC "thrombus" with the "benign" metastases, a Gunter Tulip IVC filter was placed in the infra renal IVC with incidental demonstration of upper moiety hydronephrosis within the left duplex pelvicalyceal system (Fig. 6).

Subsequently, as the sacral giant cell tumour was deemed to be unresectable, the patient received external beam radiotherapy to the sacrum. Unfortunately her disease progressed quite rapidly despite radiotherapy with an increase in both the sacral and pulmonary disease, with her demise 8 months from presentation.

Occasionally sacral giant cell tumour undergoes spontaneous dedifferentiation into osteosarcoma without prior radiotherapy; this may be the course this case followed, notwithstanding the benign surgical biopsy. A recent paper suggests that the multinucleate giant cells are recruited and have their osteoclastic activity promoted by the associated transformed fibroblastic stromal cells.

Although a previous paper describes an incidental deep vein thrombosis with sacral giant cell tumour, we believe that this is the first described case of direct giant cell tumoral thrombus within the IVC, which succinctly explains the presence of pulmonary deposits. A similar picture is well known with renal cell carcinoma.