Pulmonary calcification: scanning electron microscopic and X-ray energy-dispersive analysis.

Nine patients with chronic renal failure or neoplastic involvement of bone showed metastatic calcification in their lungs at autopsy. On light microscopy, the calcifications were shaped like threads, beads, elongated rods, or tablets, whereas on scanning electron microscopy they were either amorphous or irregularly crystalline. Energy-dispersive x-ray analysis of the calcification showed the presence of calcium and phosphorus in all cases and traces of magnesium, sulfur, and other elements in some. The calcium-to-phosphorus ratio, obtained using Hall's formula, varied from 1.406 to 2.145, which is quite similar to that of normal bone and dystrophic calcification. Calcium phosphates, therefore, seem to be the principal mineral salts in all three types of calcification. In certain diagnostic and investigative problems, a correlative analysis of structure and chemistry at the ultrastructural level, both qualitatively and quantitatively in terms of their element ratios, can be done on tissue routinely prepared for light microscopy.