Rhabdomyosarcoma. Morphologic, immunohistochemical, and DNA study.

In this study 80 cases of predominantly adult rhabdomyosarcoma are presented as follows: 20 cases of the embryonal type, 32 cases of the alveolar and 8 cases of the pleomorphic type. Additional histologic classification was performed in each type. In myotube stage the histologic picture of fetal muscles cannot be compared to the alveolar type of rhabdomyosarcoma. Desmin and sarcomeric actin are observed in 47.7% of all cases, and myoglobin and myosin in only 23.1%. The reactions were diffuse, disperse, or focal. Electron microscopic study subdivides desmin positive tumors into three groups of differentiation. DNA analysis shows that most desmin positive cells are diploid in comparison to all the tumor cells that are hyperdiploid and tetraploid.