Carbonate apatite crystals in primary normophosphatemic tumoral calcinosis

A 66-year-old woman developed firm, painless, slowly growing nodular masses over her elbows, fingers, toes, and left hip over four years. Aspiration of the elbow mass revealed a white chalky material that was shown to be carbonate apatite on infrared spectroscopy and energy dispersive X-ray spectroscopy. We discuss the classification of tumoral calcinosis and the nature of the calcium deposits. Tumoral calcinosis should be differentiated from tophaceous gout and calcium pyrophosphate dihydrate crystal deposition disease. Polarizing light microscopy and crystal analysis by X-ray and infrared spectroscopy, electron or X-ray diffraction will confirm the diagnosis. Secondary causes of tumoral calcinosis should also be excluded.