Sobre la heterogeneidad del sarcoma de Ewing óseo:

Present report deals with 23 cases of Ewing's sarcoma analysed by optical and electronic microscopical means. On the basis of the present histological criteria we believe in the existence of several morphological types of Ewing's sarcoma whose histology extends from the most undifferentiated blastemal ones to a more atypical varianteThe presence of several cell types and the existence of transitional forms between the principal cell of a blastemal nature and the more in appearance electrodense ones (dark cell) suggest that all these cells seen in the same tumor differ only in their metabolic state of maturation. On this basis a relation could be established between the number of cells present in one given type of tumor and the ultrastructural nature of this neoplasm. On this basis two maio types of Ewing's sarcoma have been identified whose characteristics are the following:Ewing typical: We have collected 15 cases of this nature in our ultrastructural analysed material. The tumors is almost exclusively composed of solid nests of blastemal cells (undifferentiated stem cells) which appear io very close contact with each other. Within similar cell structures there exist two variants: with glycogen and without glycogen. In very close relationship there are occasional dark cells (secondary cells) , with or without glycogen. In the interstitial spaces of the tumor appear isolated capillaries provided with a dense basal and without any relationship to the neoplasic cells. There exist numerousdeposits of fibrine. The reticular fibres are absent or in a very sparse number. Necrosis is abundant.Ewing atypical: In eight cases we have found sorne variations in cell distribution and morphology in relation to the first tumor group. Here, the principal cells have a more irregular nature being of a mesenchymal or histiocytic character and the glycogen content is sparse. Secondary cells are also present. Both kinds of cells appear isolated or located in groups or compact nests as typical Ewing do. In the interstitial spaces the vessels have thick basals and the reticular fibres are more abundant. Some cells of mesenchymal nature are provided with filaments in cytoplasmic, bundles associated to mithocondria. The histocytic diflerentiated ones show a very well developed RER with cysternae in functional activity. There are lysosomes inside its cytoplasm.

Present report deals with 23 cases of Ewing's sarcoma analysed by optical and electronic microscopical means. On the basis of the present histological criteria we believe in the existence of several morphological types of Ewing's sarcoma whose histology extends from the most undifferentiated blastemal ones to a more atypical varianteThe presence of several cell types and the existence of transitional forms between the principal cell of a blastemal nature and the more in appearance electrodense ones (dark cell) suggest that all these cells seen in the same tumor differ only in their metabolic state of maturation. On this basis a relation could be established between the number of cells present in one given type of tumor and the ultrastructural nature of this neoplasm. On this basis two maio types of Ewing's sarcoma have been identified whose characteristics are the following:Ewing typical: We have collected 15 cases of this nature in our ultrastructural analysed material. The tumors is almost exclusively composed of solid nests of blastemal cells (undifferentiated stem cells) which appear io very close contact with each other. Within similar cell structures there exist two variants: with glycogen and without glycogen. In very close relationship there are occasional dark cells (secondary cells) , with or without glycogen. In the interstitial spaces of the tumor appear isolated capillaries provided with a dense basal and without any relationship to the neoplasic cells. There exist numerousdeposits of fibrine. The reticular fibres are absent or in a very sparse number. Necrosis is abundant.Ewing atypical: In eight cases we have found sorne variations in cell distribution and morphology in relation to the first tumor group. Here, the principal cells have a more irregular nature being of a mesenchymal or histiocytic character and the glycogen content is sparse. Secondary cells are also present. Both kinds of cells appear isolated or located in groups or compact nests as typical Ewing do. In the interstitial spaces the vessels have thick basals and the reticular fibres are more abundant. Some cells of mesenchymal nature are provided with filaments in cytoplasmic, bundles associated to mithocondria. The histocytic diflerentiated ones show a very well developed RER with cysternae in functional activity. There are lysosomes inside its cytoplasm.