Actin, α-Smooth Muscle

Smooth muscle actin (SMA) identifies smooth muscle and myofibroblasts in normal, reactive and neoplastic tissue. It is used in the differential diagnosis of a sarcoma with a panel of other stains to identify leiomyosarcoma. It is also useful in the identification of myopepithelial cells in salivary glands and sweat glands, and in the detection of invasion in difficult breast lesions. It can also help separate desmoid tumors (SMA pos) from solitary fibrous tumor (SMA neg).