OBJECTIVETo investigate the histogenesis and pathologic features of pulmonary sclerosing hemangioma (SH) and its expression of thyroid transcription factor-1 (TTF-1).

METHODSSeventeen cases of pulmonary sclerosing hemangioma were reevaluated and 12 cases were immunostained with a panel of antibodies including TTF-1, EMA, cytokeratin, etc. Six cases were studied by electron microscopy.

RESULTSAll cases exhibited the classic histologic features with variable proportions of solid, papillary, hemorrhagic or hemangiomatic, and sclerotic pattern. The tumours consisted of solid sheets or aggregates of pale polygonal cells and papillae and clefts lined by cuboidal or columnar cells. Both TTF-1 and EMA expressions were observed in the surface lining cuboidal cells and the pale polygonal cells. In only one case both chromogranin and synaptophysin showed weakly positive in few polygonal cells and a small number of granules with high electron density was found in the polygonal cells by electronic microscopy.

CONCLUSIONSIt is suggested that pulmonary sclerosing hemangioma is an epithelial neoplasm derived from primitive respiratory epithelium capable of differentiating toward pneumocytes or Clara cells. The immunohistochemical markers such as TTF-1, EMA and CK play an important part in diagnosis of SH.