Case 3. Unicameral bone cyst with rapid growth

Case first posted Mon, Nov 11, 2002; by John Hunter

This is a case from Mike Tuite. He included the following clinical information:

6 year old boy who had a pelvis film done for right hip pain. The intertrochanteric lytic lesion was barely visisible on the inferior aspect of a KUB performed 8 months earlier. On MR, the lesion had several enhancing nodules within the fluid/myxoid material, as well as enhancing periostitis, but otherwise looked like a Simple Bone Cyst with thin enhancing lining. Pathology confirmed a UBC and the nodules were just benign fibrovascular tissue with occasional giant cells. We figured probably just an occult fx with early healing. P.S. they packed it with Wright Medical MIIG calcium sulfate, which completely resorbed in 4 weeks.

The question, ever see a UBC grow that fast? Pelvis as seen on KUB 8 months prior:

KUB

Initial KUB from 8 months earlier

AP Pelvis

Preop AP pelvis

Frogleg

Preop frogleg of both hips

Axial T1W 1Axial T1W 2

Axial T1W images

Cor T1W 1 Cor T1W 2

Coronal T1W images

Ax T2W 1Ax T2W 2

Axial T2W images

Cor T2W 1Cor T2W 2

Coronal T2W images

Ax T1W fat sat post Gd 1 Ax T1W fat sat post Gd 2

Axial and sagittal T1W fat sat post Gd images

Cor T1W fat sat post Gd 1Cor T1W fat sat post Gd 2

Coronal T1W fat sat post Gd images

Comments (3)

Michael Richardson, M.D. Mar 14, 2007 06:31 PM

Wow, that’s fast growth indeed. Just eyeballing it for size shows that it has doubled in diameter (which translates into 8 times the volume) over 8 months, giving a doubling time of about 80 days. I have never seen a simple cyst go this fast. About the only bone lesions that I usually see with this velocity are infections and aggressive, untreated metastases, which we know aren’t happening here. However, another thought occurs to me: to get this much bone removal so quickly means that osteoclasts have to be working hard. We know that this lesion is not a brown tumor, but could he have possibly have elevated PTH levels from occult renal or parathyroid disease?

Chris Beaulieu, M.D. Mar 14, 2007 06:33 PM

I’ve not seen a UBC grow this fast. It surprises me that the proximal femoral epiphyses get wider between the initial KUB and the AP pelvis, but I’m no peds rad. cb

Kirk Davis, M.D. Mar 14, 2007 06:35 PM

I’ve seen this case, since I was at the path conference that brought this to Mike Tuite’s attention. I agree this is growing incredibly fast if it’s a UBC. However, I’m not sure if I have ever seen a sequence of images in time that demonstrated much growth in a UBC at all, even over a longer time period. Has anyone else? My point is, is it the natural history for these things, however they form, to grow rapidly at the outset and then pretty much stabilize after that? If that were true, we might not have any reason to see them when they were smaller. I think that if this thing were the result of osteoclast action (whether an “osteoclastoma” or not), the pathologist would have seen an inordinate number of osteoclasts there.