Myofibroblasts in the stroma of metastatic pulmonary calcification in a patient with chronic renal failure

We present a case of metastatic pulmonary calcification. Histologically, deposition of hematoxyphilic materials was seen along the alveolar and vessel walls. Fibrous tissues were also seen within the alveolar lumens, resulting in intra-alveolar fibrous pneumonia. Immunohistochemically, CD34-positive perivascular adventitial fibroblasts were seen in normal alveolar septa, whereas no myofibroblasts were observed. In contrast, perivascular adventitial fibroblasts were absent in the alveolar septa of the lesion of metastatic calcification, whereas many myofibroblasts were present in the fibrous tissue within alveolar lumens. No positive cells for TGF-beta(1) were observed in the lesion of metastatic calcification, but positive cells for PDGF-BB were focally seen in adveolar epithelial cells. Finally, many myofibroblasts appear in the alveolar lumens of metastatic pulmonary calcification, and we suggest that these myofibroblasts may be derived from CD34-positive perivascular adventitial fibroblasts and PDGF-BB may be involved in the pathogenesis of surrounding fibrosis.