Stains
Actin - muscle specific

Author: Nat Pernick, M.D. (see Authors page)

Revised: 17 November 2015, last major update September 2013

Copyright: (c) 2003-2015, PathologyOutlines.com, Inc.

PubMed Search: Muscle specific actin[title]

Definition / General
  • Discovered in 1987 (Am J Pathol 1987;126:51); also called HHF35, MSA
  • Recognizes all alpha actins (skeletal, smooth, cardiac) and gamma smooth muscle actin; but not beta cytoplasmic or gamma cytoplasmic actin (the latter is also called non-muscle actin)
  • Recognizes actin expressed in all cells with muscle differentiation (cardiac, smooth and skeletal muscle), myoepithelial cells, myofibroblasts, pericytes and myogenic tumors (Am J Clin Pathol 1991;96:32)
Uses by Pathologists
Micro Images

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Endometriosis


Myofibroblastoma: breast (fig d)

Myofibroblastoma: lymph node

Prostate: normal smooth muscle stroma


Rhabdomyosarcoma: CNS, embryonal (left-fig 4; right-with anaplastic features)

Rhabdomyosarcoma: oral cavity



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Glomus tumor

Positive Staining - Normal
  • Cardiac muscle, decidua, myoepithelial cells (although calponin and vimentin may be better, Braz Dent J 2007;18:192), myofibroblasts, pericytes, skeletal muscle, smooth muscle and vascular smooth muscle
Positive Staining - Disease
Negative Staining