Spontaneous Metastatic Angiosarcoma of the Tongue in a Wistar Rat: Morphological and Immunohistochemical Characterization

A primary angiosarcoma was found in the tongue of a six-week-old female Wistar rat, sacrificed for humane reasons during the course of a four-week toxicology study. At necropsy, a nodule protruding from the dorsal part of the tongue was found. The nodule displayed microscopically, irregularly shaped vascular spaces separated by collagenous stroma. The spindle-shaped endothelial cells showed pleomorphism, hyperchromatism, and low mitotic activity; large nuclei with one or more nucleoli were present. Multiple metastases were found in the lungs, and the morphology of the cells resembled that of the primary tumor. Immunohistochemically, the primary tumor and the lung metastases were positive for von Willebrand factor and vimentin. The diagnosis of tongue angiosarcoma metastasizing to the lungs was made on the basis of microscopic and immunohistochemical findings.