[Ultrastructural study on formal pathogenesis of experimentally induced rhabdomyosarcomas (author's transl)]

During oncogenesis the rhabdomyosarcomas pass different stages of differentiation. In experimentally induced rhabdomyosarcomas the chronological sequence of cytoplasmatic changes can be analysed.

10 mg 9,10-dimethyl-1,2-benz-anthracene were injected subcutaneously or intramuscularly in the hind-paw of Wistar rats with 100 gms weight. 30, 60, 105, and 150 days later the animals were killed and specimens withdrawn. The soft-tissue was prepared for light- and electron-microscopy.

In the soft-tissue tumors, experimentally produced with DMBA, 4 different cell types can be observed, which--depending on exposition time--dominate in the histological picture: (1) The myofibrillar cells. These cells are similar to rhabdomyocytes and contain numerous cytoplasmatic fibrillae with sarcomere-like structure. (2) The myofilamentous cells. These cells contain the fibrillar structure, but without sarcomere-like arrangement. (3) The undifferentiated sarcoma cells. These cells show a pathologically changed ergastoplasm and chondrioma. (4) The matured fibrosarcoma cells are nearly similar to fibrocytes. Under the cytoplasmatic changes especially the hyperplasia of the chondrioma can be observed, in which dystrophic megamitochondriae are found. These possibly reflect the abnormal glycolysis in cancer tissue. Also mitochondrial antibodies are discussed at the form pathogenesis of this change in organelles. Regarding the change of the endoplasmatic reticulu, the annulatae lamellae can be noticed which are typical for tumor cells. Furthermore megacisterns are found, in which protein-containing material is condensed as a consequence of a disturbed synthesis and secretion.