The best preliminary diagnosis for only the soap bubbly lesion in the clavicle is what?
Aneurysmal bone cyst (ABC)
Open biopsy was performed after these radiographs, and intraoperative histology revealed giant cells. What is the first diagnosis you jump to based on that information?
Giant cell tumor. Well that was unexpected.
Just because you're so clever, what is another name for a giant cell tumor?
Now that you've expertly followed an appropriate chain of logic, go back and look at the films. Is there anything to suggest the latter diagnosis (of a brown tumor)?
Indeed. The bone density in this 30 year old is diminshed, he has distal clavicular resportion, and subperiosteal resportion along the medial aspect of the humeral neck. All classic findings suggestive of hyperparathyroidism (HPT).
A well-defined, mildly expansile lesion is observed in the distal clavicle approximately 1cm proximal to the distal articular surface. The lesion is soap-bubbly in appearance with mild cortical thinning. There is no evidence of cortical violation or overlying periosteal reaction.
Overall bone density appears moderately diminished. The acromioclavicular joint appears widened, with an indistinct distal clavicular articular surface. The cortex along the medial aspect of the humeral neck appears thinned and feathery on the external rotation view.