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SMA

Monday 19 March 2018

smooth muscle actins

PO

See also : ACTA2

Expression

- smooth muscle tumors

  • leiomyoma
  • leiomyosarcoma

- bone tumors

  • Alpha isoform of smooth muscle actin (SMA) expression has been reported in giant cell tumour of bone (GCTB) and other benign and malignant bone tumours.
  • The nature of SMA-expressing cells in bone tumours is uncertain but they are negative for desmin and caldesmon and could represent either myofibroblasts or perivascular cells, such as pericytes.
  • giant cell tumour of bone - GCTB
  • aneurysmal bone cyst - ABC
  • chondroblastoma - CB
  • chondromyxoid fibroma
  • " malignant fibrous histiocytoma " of bone (12401825)
    • MFH of bone may derive from mesenchymal stromal cells in bone marrow and has a more myofibroblastic differentiation than soft tissue MFH.
  • osteosarcomas
    • ezrin -EZR and alpha-smooth muscle actin are predictive IHC prognostic markers for patients with an osteosarcoma. (17786474)

IHC marker for diagnosis

- SMA identifies smooth muscle cells and myofibroblasts in normal, reactive or neoplastic tissue. (Am J Respir Cell Mol Biol 1999;20:582)(Am J Dermatopathol 2006;28:105)

- SMA identifies myoepithelial cells in normal, neoplastic or diseased breast, salivary glands or sweat glands. (Anticancer Res 2003;23:4175)

  • It may be helpful to rule out invasion.
  • It may be particularly important in cytology specimens.

- SMA identifies pericytes to correlate with hematogenous metastasis and prognosis. (Oncology 2005;69:159)

- SMA can help distinguish pleuropulmonary desmoid tumors (SMA+) from solitary fibrous tumor (SMA-, Arch Pathol Lab Med 2006;130:1503).

- In breast papillary anomalies, p63 is more sensitive and specific because smooth muscle actin - SMA also stains stromal cells (J Clin Pathol 2007;60:315).