Metastatic calcification or calcinosis is caused by the deposition of calcium salts in the lung tissue due to a systemic increase in serum calcium levels. It is often bilateral and diffuse, but may be focal. Most patients have no symptoms, but rarely patients may develop respiratory failure. Currently chronic renal insufficiency with hemodialysis is the most frequent setting in which this condition develops, but traditionally it has been seen in association with hyperparathyroidism and paraneoplastic syndromes. Metastatic calcification may also be observed in the lungs of patients with sarcoidosis, systemic sclerosis, hypervitaminosis D, and cancers with extensive bone disease.

Metastatic calcification should be distinguished from the much more commonly occurring dystrophic calcification. Dystrophic calcifications are typically found in scarred or necrotic tissue caused by previous infections or injuries. Although they are occasionally detected on radiologic studies or catch the pathologist’s eye, they are not clinically important. Ossification or bone formation may also arise in dystrophic calcifications and also is of no clinical significance.