Embryonal rhabdomyosarcoma in nude mice and in vitro

A transplantable tumor strain designated YNnu and a cultured cell line designated YN were established from the human paratesticular rhabdomyosarcoma of a 15-year-old boy. In vitro the cells showed ultrastructural features of immature mesenchymal cells, and a few cells were labeled by antibodies to myoglobin and/or desmin. In nude mice, the cells became to contain numerous myofibrils with Z-bands, and considerable number of cells reacted with anti-myoglobin and/or anti-desmin antibodies. We conclude that spindle-shaped or small round cells are the most immature rhabdomyoblast with multiplicity for cellular differentiation.