[The ultrastructure of human rhabdomyosarcomas]

As a result of exploration of the ultrastructure of 5 human rhabdomyosarcomas it was shown that, if present in the cytoplasm, cells of fibrillar bundles consisting of filaments of two types (40-60 A and 100-150 A) and regular aggregations of Z-like bands type present a reliable diagnostic sign of the myogenic origin of tumors. A possibility to determine such undifferentiated microfibrillae in electrone-microscopic study makes it rational to use the method as an adjunct in association with light optics to diagnose malignant soft tissue tumors of occult genesis.