Iron content of pigmented villonodular synovitis detected by computed tomography.

Pigmented villonodular synovitis is a rare lesion in which iron is accumulated. A CT scan performed on one such lesion demonstrated significantly increased attenuation values. We have calculated the amount of iron which would have to be added to muscle tissue in order to produce this increase in density. We have also measured the iron content directly. The close agreement of these two figures suggests that the observed density increase is due to the iron content of the lesion.