[A case of pulmonary epithelioid hemangioendothelioma that required differentiation from malignant mesothelioma]

A 77-year-old woman presented with a 3-month history of right chest pain and a low-grade fever. Right pleural effusion had been detected at another hospital. Her chest CT scan revealed right pleural effusion, right pleural thickening, and bilateral multiple lung nodules. No specific findings were obtained from an examination of the pleural effusion. Thoracoscopic pleural and lung biopsies were conducted. Histologically, the tumor had an infiltrative growth pattern in the fibrously-thickened parietal pleura, visceral pleura, and lung parenchyma. The tumor was composed of epithelioid and spindle cells, and in some sections, the tumor cells had intracytoplasmic vacuoles, and had formed an immature vascular lumen. Proliferation in a papillary fashion in the alveolar spaces and vascular involvement of tumor were also seen. Immunohistochemically, the tumor cells were positive for factor VIII-related antigen, CD31, and CD34, and negative for calretinin and WT-1. The tumor was therefore diagnosed as pulmonary epithelioid hemangioendothelioma (PEH), which is a rare, low-to-moderate grade vascular tumor of the lung. This disease should be included in the differential diagnosis together with malignant pleural mesothelioma, in cases demonstrating unusual pleural thickening.