Musculoskeletal images. Aneurysmal bone cyst of pelvis
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* Henry K. Cheah
* Anthony M. Griffin
* Lawrence M. White

A 24-year-old man presented with a 3-week history of increasing urinary urgency and dysuria and the presence of a right lower quadrant mass. Fifteen months earlier he had sustained a direct blow to the hip while skiing. His hip had been progressively painful during weight bearing over the past 2 months.

Physical examination and magnetic resonance imaging (MRI) revealed a large right lower quadrant mass fixed to the pelvis. Computed tomography (CT) showed a that the mass originated from the right acetabulum and superior pubic ramus (Figs. 1 and 2). An open biopsy of the pelvis confirmed the pathological diagnosis of aneurysmal bone cyst (ABC).

![FIG. 1](http://canjsurg.ca/https://www.canjsurg.ca/content/cjs/42/6/411/F1.medium.gif)

[FIG. 1](http://canjsurg.ca/content/42/6/411/F1)

FIG. 1 
An axial computed tomography image shows the contrast medium in the bladder being displaced by the tumour (arrows).

![FIG. 2](http://canjsurg.ca/https://www.canjsurg.ca/content/cjs/42/6/411/F2.medium.gif)

[FIG. 2](http://canjsurg.ca/content/42/6/411/F2)

FIG. 2 
A coronal magnetic resonance image, demonstrating the mass (arrows) originating from the right superior pubic rami.

The patient underwent 2 embolization procedures in an attempt to shrink the tumour (Figs. 3 and 4). Despite occlusion of the feeding vessels, no significant change in the size of the tumour was detected on post-embolization CT. Subsequently, the lesion was resected and the acetabulum reconstructed. Fig. 5 is a plain radiograph of the patient’s pelvis several months postoperatively.

![FIG. 3](http://canjsurg.ca/https://www.canjsurg.ca/content/cjs/42/6/411/F3.medium.gif)

[FIG. 3](http://canjsurg.ca/content/42/6/411/F3)

FIG. 3 
Pre-embolization angiogram showing extensive feeding of the tumour by pelvic vessels.

![FIG. 4](http://canjsurg.ca/https://www.canjsurg.ca/content/cjs/42/6/411/F4.medium.gif)

[FIG. 4](http://canjsurg.ca/content/42/6/411/F4)

FIG. 4 
The post-embolization angiogram.

![FIG. 5](http://canjsurg.ca/https://www.canjsurg.ca/content/cjs/42/6/411/F5.medium.gif)

[FIG. 5](http://canjsurg.ca/content/42/6/411/F5)

FIG. 5 
A plain radiograph of the patient’s pelvis postoperatively. Cement was used to reconstruct the bony defects in the pelvis.

The large soft-tissue mass (with relatively small bone involvement) is unusual for an ABC. Embolization was critical to the safe removal of this lesion. It is possible that bone trauma 15 months before to presentation initiated the growth of this tumour.

## Footnotes

*   Section Editor: Robert S. Bell, MD

*   Submissions to Surgical Images, musculoskeletal section, should be sent to Dr. Robert S. Bell, University Musculoskeletal Oncology Unit, Ste. 476, 600 University Ave., Toronto ON M5G 1X5; fax 416 586-8397.