Actin isoform pattern expression: a tool for the diagnosis and biological characterization of human rhabdomyosarcoma

Abstract.

The diagnosis and characterization of rhabdomyosarcoma requires the use of combined histological and immunohistochemical criteria due to the variety of its histological patterns. The identification of actin isoform expression is accepted as a useful adjunct to the diagnosis and classification of soft tissue tumors. Using a new antibody specific for α-cardiac actin, obtained according to a recently described strategy for the production of polyclonal antibodies against actin isoforms [9], we have analyzed a series of 17 rhabdomyosarcomas, including all histological subtypes. In addition, we have evaluated the presence in these tumors of α-skeletal and α-smooth muscle actins. All specimens examined revealed a positive immunostaining for α-cardiac actin. Tumoral cells of eight cases also expressed α-smooth muscle actin and only three cases (all embryonal subtypes) were positive for α-skeletal actin. Our results indicate that immunohistochemical screening for α-cardiac actin expression is a useful tool for the diagnosis of rhabdomyosarcoma. They also suggest that the expression of α-skeletal actin is valuable in determining the subtype and possibly the state of differentiation of these tumors.