Immunohistochemical studies of rhabdomyosarcoma.

We performed immunoperoxidase studies in 29 cases of rhabdomyosarcoma from the Intergroup Rhabdomyosarcoma Study I using antisera against actin, myosin, myoglobin, alpha-actinin, and tropomyosin. Although each of these antisera reacted with some of the tumors, none reacted with all of the tumors, and some tumors showed no reactivity. Antimyosin reacted with more tumors than any of the others, while antiactin and antimyoglobin were about equally sensitive. Antitropomyosin and anti-alpha-actinin reacted with few of the tumors. The better-differentiated tumors were more likely to react compared with the poorly differentiated tumors.