The endothelium is the inner surface of blood vessels and lymph nodes. Endothelial cells are constantly destroyed and replaced by new cells. They secrete elastic fibers that form a network of fibers and cells called the extravasal matrix (EVM). In addition, these cells express a variety of cell-cell adhesion molecules, including selectin protein, which plays a key role in the process of recruitment of mononuclear phagocytes through the circulatory system. These mononuclear cells are key elements in the pathogenesis of rheumatoid arthritis, and a defect in this system may explain why patients with rheumatoid arthritis have a deficiency of endothelial cells and a marked increase in extravasal matrices.
Synovial endotheliomas (ES) are neoplasms arising from elastic fibers diffusely distributed in soft tissues and nearby structures. ES represents vessels