Angiosarcoma : D2-40
A subset of angiosarcomas (usually located on scalp and face) demonstrate true lymphatic differentiation. The histologic features include anastomosing lymphatic channels lined by hobnail endothelial cells, absence of red blood cells in the lumens, lymphoid aggregates in the stroma, and positivity for lymphatic markers (D2-40, prox-1, and VEGFR-3). D2-40 (Podoplanin) is a transmembrane glycoprotein that is expressed by many cell types, including lymphatic endothelial cells, glomerular podocytes, choroid plexus epithelium, type 1 alveolar cells, osteoblasts, and mesothelium. It is regulated by the homeobox gene Prox1. D2-40 is expressed by a variety of tumors such as endothelial-derived (including angiosarcomas), mesenchymal, germ cell, and glial neoplasms. It is helpful in differentiating mesotheliomas (frequently positive) from adenocarcinomas (usually negative). This image shows strong D2-40 immunoreactivity in angiosarcoma. Image courtesy of: Brendan Dickson, MD, Dept. of Pathology, University of Toronto, Ontario, Canada; Used with permission.