Sclerosing Hemangioma of the Lung

Abstract

Sclerosing hemangioma of lung is an unusual neoplasm with distinctive morphological features. Although its histogenesis has been debated for decades, the current concept is that this is a tumor of cells with features most closely resembling type II pneumocytes. The tumor has 2 separate cellular components (surface cells and round cells) and 4 different growth patterns (solid, papillary, sclerotic, and hemorrhagic), which may be present in various degrees from one tumor to another. Both surface and round cells stain positive for TTF-1 and epithelial membrane antigen, whereas the surface cells stain strongly positive for cytokeratins and for surfactant proteins A and B. Round cells generally stain negative for cytokeratins and surfactant proteins. Ultrastructurally, the surface cells have features of type II pneumocytes with well-formed lamellar bodies, whereas the round cells are more primitive and contain dense core granules and microtubules. Despite the name of the tumor, vascular differentiation is not observed. Sclerosing hemangioma typically presents as a unilateral pulmonary nodule, but multiple and bilateral examples have been reported. Although this tumor typically behaves in a benign fashion with long-term survival expected after surgical resection, cases with lymph node metastases and more aggressive clinical behavior have been reported. This tumor has the potential for confusion with other more common and aggressive lung neoplasms, especially in cytological specimens. We report herein a case of sclerosing hemangioma of the lung with lymph node metastasis and review the literature on this unusual neoplasm.