Anti-muscle-specific actin

All squamous carcinomas of the skin lack S-100 protein, chromogranin, synaptophysin, CD99, CD 15, and CD57. Further, reactivity with HMB-45 or anti-melan-A is consistently absent, as are desmin and muscle-specific isoforms of actin in most spindle-cell forms of these neoplasms. ... 

SMA Smooth muscle antibodies were first described by G.D. Johnson et al. (1965). They mostly possess anti-actin (generally F-actin) specificity, predominantly of the IgG type. Antibodies against troponin and a-actin may also be present. There is great heterogeneity, and a mixture of different antibodies can almost always be found. Evidence of anti-actin antibodies has a high diagnostic value, particularly with a titre of > 1 640 and in the presence of an IgG type. (s. fig. 5.12) (s. p. 119)... 

Cytokeratin cocktail antibodies can be used to identify MECs (in addition to CK14 and CK17). However, because of the proximity of MECs to acinar cells, differentiation is difficult because these cocktails also immu-nostain acinar cells. Anti-smooth muscle actins react with stromal myofibroblasts in addition to MECs " and thus are not specific for MECs. The cross-reaction with myofibroblasts makes it difficult to identify MECs specifically, especially for ductal carcinoma in situ (DCIS) cases in which periductal stromal desmoplasia may exist. 

Gugliotta P, Sapino A, Macri L, et al. Specific demonstration of myoepithelial cells by anti-alpha smooth muscle actin antibody. J Histochem Cytochem. 1988 36 659-663. 

Autoimmune hepatitis (AIH). Chronic autoimmune-mediated hepatic inflammation characterized by antinuclear (ANA), smooth muscle (SMA)/anti-F-actin, liver-kidney microsomal (LKM), and soluble liver antigen (SLA) antibodies. Autoimmune hepatitis constitutes 10-20% of all cases of chronic hepatitis, ft may be idiopathic (Alff type 1, 2, and 3), part of autoimmune polyendocrine syndrome type 1 (APECED hepatitis), or drug-induced. See also -liver-kidney microsomal antibodies, liver-specific antigens. 

---