Sclerosing hemangioma of the lung. An epithelial tumor composed of immunohistochemically heterogenous cells.

Lung tissues from 16 patients with pulmonary sclerosing hemangioma were studied with the use of serial sections and immunoperoxidase staining for surfactant apoprotein, secretory component (SC), and epithelial membrane antigen (EMA). The cells lining papillary projections or cystic spaces were stained with surfactant apoprotein, SC, and EMA. Characteristic round stromal cells, which were considered to be the main component of the sclerosing hemangioma, consisted of immunohistochemically heterogenous cells, that is, positive findings were attained with all three antigens, surfactant apoprotein- and EMA-positive ones, SC- and EMA-positive ones, only EMA-positive ones, and all three negative. When investigating the immunoreactivity of neoplastic type II pneumocytes in bronchioalveolar cell carcinoma and hyperplastic ones in nonneoplastic pulmonary disorders, the authors found that almost all the neoplastic type II pneumocytes had all three antigens. Many of the hyperplastic and normal type II pneumocytes, however, were stained with surfactant apoprotein and EMA but not with SC. The authors' findings add further support for the proposal that sclerosing hemangioma of the lung is epithelial in origin. In view of the various staining patterns found in the stromal cells, sclerosing hemangioma probably consists of immunohistochemically heterogenous epithelial cells. The staining pattern of the cells lining papillary projections or cystic spaces was similar to that of neoplastic type II pneumocytes rather than that of hyperplastic type II pneumocytes.