A case of pneumocytoma (so-called sclerosing hemangioma) with lymph node metastasis.

A case of "sclerosing hemangioma" (pneumocytoma) of the lung with lymph node metastasis is reported. A 22-year-old Japanese man was found to have a well-defined round lesion in the right lung (S7), which increased in size slightly during a 2-year follow-up period. He underwent right lower lobectomy with a preoperative diagnosis of a benign lung tumor. The pulmonary tumor revealed histological features characteristic of "sclerosing hemangioma" of the lung, in addition to which there were many large polygonal foamy cells, forming tubular or papillary structures. These cells were found by electron microscopy to contain numerous cytoplasmic lamellar bodies and showed a positive reaction with anti-surfactant apoprotein antibody immunohistochemically. Therefore, they were considered to be cells differentiating toward type II pneumocytes. Review of 21 typical "sclerosing hemangiomas" disclosed a few or some such foamy cells in 10 cases. A single hilar lymph node was the site of microscopic metastases, which consisted of "large clear foamy cells" and smaller polygonal or round cells with slightly eosinophilic cytoplasm, both of which were components of the pulmonary "sclerosing hemangioma." This case supports the theory that "sclerosing hemangioma" is a neoplasm of type II pneumocyte lineage. Although it is said to be benign, rare cases apparently show metastatic potential.