Pulmonary sclerosing hemangioma of the lung. A type II pneumocytoma by immunohistochemical and immunoelectron microscopic studies.

Three cases of pulmonary sclerosing hemangioma were studied by immunohistochemical and immunoelectron microscopic methods using a panel of antibodies. Six cases of adenocarcinoma of the lung, three cases of normal mesothelium, and three cases of mesothelioma were used as controls. The cytoplasm of some of the sclerosing hemangioma tumor cells was positive for the anti-lung surfactant apoprotein monoclonal antibody (PE-10). These cells were the pale cells of the solid areas, the cells covering the papillary projections, and the cells lining the cleft-like spaces. These cells also were positive for conventional epithelial cell markers. Some cells also were positive for vimentin. Electron microscopic study showed that the predominant cell was a poorly differentiated pneumocyte. Immunoelectron microscopic study also demonstrated that PE-10 existed in the rough endoplasmic reticulum of some of the cells in the solid areas, in the same way as normal type II pneumocytes. We concluded that the sclerosing hemangioma is an epithelial tumor with differentiation towards type II pneumocytes.