Matrix metalloproteinase-1 expression in splenic angiosarcoma metastasizing to the serous membrane.

Angiosarcoma involving the serous membrane may mimic mesothelioma; therefore, the term "pseudomesotheliomatous angiosarcoma" has been suggested for this entity. However, the pathogenesis of pseudomesotheliomatous angiosarcoma remains unclear. Here, we report an autopsy case of splenic angiosarcoma, which systemically metastasized to the serous membrane of both the peritoneum and pleura, closely resembling a mesothelioma. The spindle-shaped tumor cells exhibited marked invasion of the lymphatic vessels and invaded the serous membrane causing thickening of the fibrous tissues like desmoplastic mesothelioma. In the present case, immunohistochemical staining showed that the tumor expressed not only the endothelial cell markers, such as CD31, vascular endothelial growth factor receptor 3, and podoplanin (D2-40), but also matrix metalloproteinase-1 (also known as collagenase-1), which is known to increase the invasiveness of mesothelioma cells. MMP-1 expression was not observed in the other cases of angiosarcoma, examined. This tumor might systemically metastasize to the serous membrane via the lymphatic route and might generate the fibrous stroma aided by the matrix metalloproteinase-1.