Alpha Actin Antibody / ACTA2 (smooth muscle)

Actin is a major component of the cytoskeleton and is present in most cell types. This Smooth muscle actin antibody is highly specific to the smooth muscle form. Its epitope lies in the first four N-terminal amino acids. The Smooth muscle actin antibody does not stain cardiac or skeletal muscle; however, it does stain myofibroblasts and myoepithelial cells. It could be used together with antimuscle specific actin and myogenin in making a diagnosis of smooth/skeletal muscle tumors. In most cases of rhabdomyosarcoma, this smooth form antibody yields negative results whereas antimuscle specific actin and myogenin are positive. Leiomyosarcomas are positive only with antimuscle specific actin and are negative with anti-myogenin.