A so-called sclerosing hemangioma of the lung was removed from a 45-year-old woman after a follow-up of 15 years. In addition to the histology of solid, hemorrhagic, papillary and sclerosing patterns, two types of various-sized, irregularly shaped spaces were found to be lined by either small cells with a high N/C ratio (L1 cells) or large, eosinophilic or foamy cells (L2 cells). These spaces (L1 and L2 spaces) were often alternately arranged. Clusters of L1 cells or L2 cells were also observed in solid-pattern areas with or without lumen formation. Eosinophilic nuclear inclusion bodies (NIB) were exclusively found among L2 cells. L2 cells as well as NIB-containing cells showed an immunohistochemical reactivity similar to that of type II pneumocytes (i.e., positive cytokeratin, epithelial membrane antigen (EMA), surfactant apoprotein, alpha-1-antitrypsin and nonspecific cross-reacting antigen). L1 cells were immunohistochemically similar to solidly growing cells (S cells) which showed positive EMA, alpha-1-antitrypsin and vimentin. These results are consistent with the view that NIB are a good marker for type II pneumocytes in so-called sclerosing hemangioma, and that the two characteristic types of spaces were formed in different ways, thus favoring the theory that S cells are an immature form of type II pneumocytes.