[A benign neuroendocrine tumor of the lung: study on the origin of the so-called sclerosing hemangioma of the lung].

31 cases of the so-called sclerosing hemangiomas of the lung were studied by light microscope, immunohistochemical and electron microscopy. This tumor is benign and has 3 histologic patterns: papillary, hemangioma-like and solid type. Characteristic morphology being uniform round tumor cells, lying within the stroma in different patterns and regarded as the major component of sclerosing hemangioma, expressing neuroendocrine markers which include chromagranin A, neuron-specific enolase, ACTH, growth hormone, calcitonin and gastrin. Only a few tumor cells were positive for epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA), all the tumor cells were negative for keratin (Polyclonal, Z622) stain. However, in contrast to the round tumor cells, the cells lining papillary projections or cystic spaces, which presented as normal or hyperplastic alveolar cells, stained positive for keratin, EMA and CEA but negative for neuroendocrine markers. Both the surface cells and tumor cells were negative for Factor VIII-related antigen and alpha 1-AT. Therefore, pulmonary sclerosing hemangioma was regarded to be a benign tumor originating from the neuroendocrine cells of the lung and we suggest that it be renamed as benign neuroendocrine tumor of the lung (LBNET). This viewpoint has not been previously reported in the literature.