Heterotopic ossification in the pulmonary metastases of gastric adenocarcinoma: report of a case and review of the literature.

A case of heterotopic ossification in the pulmonary metastases of an adenocarcinoma of the stomach is presented. This report represents the second known case in the world literature. Three cases with ossification in the primary tumor of the stomach and three cases of colorectal adenocarcinoma with ossification in the pulmonary metastases have been reported. The findings in these reports are reviewed and compared with those in the present case. The observations in these cases are consistent with the theory that heterotopic ossification in tumors and/or their metastases is due to metaplasia of fibroblasts induced by the presence of malignant cells.