Endothelioma

ENDOTHELIOMA, a tumor arising from the endothelium of blood or lymphatic vessels during the process of pathological, blastomatous growth (hemangioendotheliomas and lymphangioendotheliomas). The histogenesis of endothelioma cannot always be considered clear, due to the fact that some endotheliomas are morphologically indistinguishable from tumors of epithelial origin. Furthermore, the difficulty lies in the fact that structures resembling an atypical network of vascular endothelium can apparently arise not from the endothelium, but from mesenchymal cells in general, through the metamorphosis of these cells into vascular wall cells, i.e., into endothelium. In particular, the term "angioplasty sarcoma" emphasizes such a possibility. In other words, an endothelioma may not arise from the endothelium; rather, the latter and the vessels as a whole may form from amorphous or syncytial mesenchyme during the process of blastomatous growth and development. Recently, the term endothelioma has been used much less frequently than before, as a number of tumors previously considered endotheliomas are no longer classified as such. For example, at present, one does not speak of endotheliomas of the meninges, as it has been proven that the covering cells of the brain membranes belong to the neuroepithelium. In connection with the classification of the covering cells of the body's serous cavities as mesothelium, corresponding malignant tumors of the pleura, peritoneum, and pericardium have ceased to be called endotheliomas, with a preference for designating them as carcinomas. Finally, what was previously classified as endothelioma in salivary gland tumors is now associated with the epithelium of the glands. Macroscopically, endotheliomas appear as rounded nodes of varying, mostly dense consistency; their color ranges from pale gray or whitish to gray-red and red, depending on whether we are dealing with the lymphatic or blood vessel systems, the quantity of the latter, etc. The cross-section of an endothelioma is often clearly spongy or porous. Clinically, endotheliomas can be benign or malignant neoplasms, and it is not always easy to establish this morphologically; sometimes one can clearly see the infiltrating growth of the endothelioma. In particular, malignant polyps (fibromas) of the nasopharynx often turn out to be such infiltrating hemangioendotheliomas. Lymphangioendotheliomas are observed most often in the skin, ovaries, testicles, bones, and other organs. Sometimes the site of development for lymphangioendotheliomas is typical lymphangiomas (see). Hemangioendotheliomas are also observed in the skin, and more rarely in various other organs, with the tumor cells arranged either in solid cords or in thin capillary tubes containing blood. Pictures of hematopoiesis within the vessel lumens are also observed. Combinations with angiomas or the transition of the latter into hemangioendotheliomas are possible. Among the histological varieties of endothelioma, one should point out adenomatous and cystic forms, where the vascular endothelium takes on a cuboidal or cylindrical shape, while the lumens stretch out in a cystic manner. Sometimes the lumens of the tubes turn out to be filled with a homogeneous colloid-like or mucous content (cylindromatous endothelioma). The stroma of the tumor can also undergo mucous metamorphosis. The formation of psammoma bodies can also occur in endotheliomas (psammomatous endothelioma). The treatment for endothelioma is surgical. Regarding endothelioma of the serous membranes, see Mesothelioma and Perithelioma.