6533b7d9fe1ef96bd126c14f

RESEARCH PRODUCT

Ultrastructure of vascular neoplasms

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Summary The vascular tumors are morphologically recognized by their ability to configurate complete or atypical angiomatous structures. Based on our personal experience of 42 cases of benign and malignant angiomatous tumors, we discussed several aspects of their histogenesis and its morphology when studied with transmission and scanning electron microscopy. Therefore, a survey of the normal histology was developed based not only on normal adult histological structures but also on reparative tissues, as in chronic inflammatory reactions of the gingival mucosa, regenerative tissue of wounds and in chronic osteomyelitis. Supported by morphological arguments, we postulate the existence of several endothelial cell subpopulations, which are involved through several ways in tumoral angiogenesis. This fact is clearly seen in benign capillary angioma, in pseudopyogenic granuloma of the skin and in cellular angioma of infancy. Among the malignant vascular tumors, the hemangiopericytoma shows a large cell heterogeneity, dilating from well developed pericytes to fusocellular and anaplastic ones; well differentiated hemangiopericytoma keeps an epithelial-like appearance and its cells surrounded by basement membranes. It seems possible to distinguish an hemangioendothelioma from an angiosarcoma (hemangiocarcoma). Both are angiogenic neoplasms of malignant nature, but the first is mainly composed by transformed endothelial cells of a mesenchymal nature, similar to those seen in embryonic angiogenesis. The second tumor type possesses not only endothelial cells but also mesenchymal angioblasts from which other cells derivatives are conformed as atypical pericytes. Furthermore, in some cases angiosarcoma displays embryonic metaplastic hematopoiesis (erythropoiesis) inside the neoformed stroma. Histogeneis of Kaposi sarcoma of the skin remains a matter of controversy. The histiocytic endothelial cells could be considered as the primitive endothelial cell subpopulation from which this tumor group could be originated. Bone vascular tumors adopt a more specific texture. Particular emphasis is given to the angiogenic variant of Ewing's sarcoma, from which three cases have been isolated among the 219 neoplasms reviewed.