Tissue culture as a diagnostic technique for soft-tissue sarcoma of childhood.

A case of childhood small cell undifferentiated sarcoma was grown in vitro in a serum-free culture medium. In vivo the tumor showed no evidence of differentiation by light microscopy, electron microscopy, and immunoperoxidase staining for myoglobin or skeletal muscle myosin. After growth in vitro for two weeks in a defined culture medium, the tumor cells formed myotubes and demonstrated ultrastructural myogenic differentiation. This case demonstrates the use of the tissue culture as a diagnostic aid in the recognition of childhood small cell undifferentiated sarcomas. It also raises questions regarding the origin of these tumors and the ability of in vitro growth to induce differentiation.