Antimyosin and antirhabdomyoblast sera: their use for the diagnosis of childhood rhabdomyosarcoma.

Antisera against myosin of human normal skeletal muscle and against rhabdomyoblasts of autopsy-proved rhabdomyosarcoma were raised in white rabbits, purified, and assessed for their usefulness in the diagnosis of childhood rhabdomyosarcoma. The specificity of the antisera was tested by both immunofluorescence and immunoperoxidase methods in seven cases of autopsy-proved rhabdomyosarcoma, five of malignant lymphoma, three of neuroblastoma, and two of Ewing's sarcoma. Antimyosin serum tested positive for all cases of rhabdomyosarcoma and negative for other types of tumor. Antirhabdomyoblast serum was positive in all cases of rhabdomyosarcoma and cross-reacted with cases of neuroblastoma and Ewing's tumor, although the intensity of staining was much decreased. Our results indicate that antimyosin serum is specific for childhood rhabdomyosarcoma and can be used to differentiate this from other childhood "round cell" tumors.