Actin muscle specific

Synonyms: Muscle Specific Actin, HHF35, MSA

by Jan Klos

Background

Actins are a family of multi-functional proteins that form microfilaments and are present in all eukaryotic cells. They are present as a part of cytoskeleton (microfilaments) and as a part of the contractile apparatus in muscle cells. Actin proteins participate in many important cellular processes, including muscle contraction, cell motility, cell division, vesicle and organelle movement, cell signaling, and the establishment and maintenance of cell junctions and cell shape.

Positive staining in normal cells and tumors

The antibody recognizes an epitope common to alpha-skeletal, alpha-cardiac and gamma-smooth muscle actins, but not other actin types. Positive staining is present in normal skeletal muscles, cardiac muscle, normal smooth muscles, myoepithelial cells and myofibroblasts as well as in tumors with differentiation in these directions.

Staining pattern

Staining pattern is cytoplasmic.

Application

  • Identification of skeletal muscle and smooth muscle cells
  • Classification of tumors with differentiation towards smooth or skeletal muscles, myofibroblasts, pericytes and myoepithelial cells
  • More sensitive in cases of rhabdomyosarcoma and in some cases of leiomyosarcoma than SMA (Smooth Muscle Actin)
  • Is more often positive than SMA in cases of Polymorphous Low Grade Adenocarcinoma and Salivary Duct Adenocarcinoma of salivary glands
  • Sarcomatoid mesothelioma is positive for MSA (Muscle Specific Actin) and SMA in 20-30% cases
  • Complementary to SMA in classification of spindle cell proliferation in panel

Selected references

  1. Gannon BR1, Dexter DF, Petsikas D, et al. Mediastinal thymolipoma: a rare occurrence with striated myoid cells. Tumori. 2007 Mar-Apr;93(2):198-200.
  2. Ghosn SH1, Radfar A, Stefanato CM. Skeletal muscle regeneration: report of a case presenting as a cutaneous nodule following blunt trauma to the lip. J Cutan Pathol. 2007 Apr;34(4):352-4.
  3. https://en.wikipedia.org/wiki/Actin
  4. https://app.immunoquery.com/engine/abpanel?abs=Actin-HHF-35
  5. Kung IT1, Thallas V, Spencer EJ, et al. Expression of muscle actins in diffuse mesotheliomas. Hum Pathol.1995 May;26(5):565-70.
  6. Mitani Y1, Ueda M, Komatsu R, et al. Vascular smooth muscle cell phenotypes in primary pulmonary hypertension. Eur Respir J. 2001 Feb;17(2):316-20.
  7. Riedlinger WF1, Juraszek AL, Jenkins KJ, et al. Pulmonary vein stenosis: expression of receptor tyrosine kinases by lesional cells. Cardiovasc Pathol. 2006 Mar-Apr;15(2):91-9.