ABSTRACT
<p><b>OBJECTIVE</b>To investigate the significance of thyroid transcription factor-1 (TTF-1) in the histogenesis of pulmonary sclerosing hemangioma (PSH).</p><p><b>METHODS</b>With clinicopathologic data of 36 PSH patients obtained, all specimens were stained by immunohistochemical method with a panel of antibodies including TTF-1, SpA, CK, EMA, F-VIII, CD34, Claretinin, HBME, synaptophsin, chromogranin, actin and S-100.</p><p><b>RESULTS</b>The patients were mostly women with a mean age of 46.7 years and a median age of 48 years. All lesions were solitary and well circumscribed with a mean size of 3.3 cm and a median size of 3 cm. No multiple or metastasis was found. Surface cells (SC) and round cells (RC) were showed in PSH, with more than 90% showing TTF-1 and EMA by immunohistochemical method. CK and SpA were showed in SC, which were not showed in RC. Neuroendocrine cells scattered within RC of PSH were detected in a few cases. Mesothelial, vascular endothelial, neuroendocrine, and myoepithelial markers by immunohistochemical method were negative.</p><p><b>CONCLUSION</b>Pulmonary sclerosing hemangioma, a benign tumor, originates from the alveolar pneumocytes. Its surface cells are more mature, while the round cells, being primitive respiratory epithelia, may undergo phenotypic differentiation and evolve into mucinous glands or neuroendocrine structure among other components.</p>