Difference between revisions of "Pleomorphic adenoma"

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*Proliferation of myoepithelium and epithelium (ductal cells) in mesenchymal stroma.
*Proliferation of myoepithelium and epithelium (ductal cells) in mesenchymal stroma.
**Cells in ducts = epithelial.
**Cells in ducts = epithelial.
**Cells not in ducts = myoepithelial.<ref name=IW_10jan2011>IW. 10 January 2011.</ref>
**Cells not in ducts = myoepithelial.<ref name=IW_10jan2011>Weinreb I. 10 January 2011.</ref>
*Mesenchymal stroma - '''important feature'''.
*Mesenchymal stroma - '''important feature'''.
**May be any of following: [[myxoid stroma|myxoid]], mucochondroid, hyalinized, osseous, fatty.
**May be any of following: [[myxoid stroma|myxoid]], mucochondroid, hyalinized, osseous, fatty.
Line 31: Line 31:


Notes:
Notes:
*Mesenchymal stroma not required for diagnosis -- if >5% ducts.<ref name=IW_10jan2011>IW. 10 January 2011.</ref>
*Mesenchymal stroma not required for diagnosis -- if >5% ducts.<ref name=IW_10jan2011>Weinreb I. 10 January 2011.</ref>
**No chondroid stroma ''and'' <5% ductal cells = '''[[myoepithelioma]]'''.
**No chondroid stroma ''and'' <5% ductal cells = '''[[myoepithelioma]]'''.
*Complete excision is often elusive; stating "completely excised" on a surgical pathology report is unwise.
*Complete excision is often elusive; stating "completely excised" on a surgical pathology report is unwise.

Revision as of 15:29, 10 November 2013

Pleomorphic adenoma, abbreviated PA, is a very common benign salivary gland tumour.

General

Features:

  • Very common - approx. 60% of parotid gland tumours.[1]
  • May transform into a malignant tumour.
    • Other benign salivary gland tumours do not do this.
  • Only benign childhood salivary gland tumour of significance.

Weinreb's dictums

  1. Most common salivary tumour in all age groups.
  2. Seen in all sites (unlike other benign tumours).
  3. Recurrence and malignancy risk (unlike other benign salivary gland tumours).
  4. Any part of a tumour that looks like PA makes it a PA.

Gross

  • May be cartilaginous appearing.

Image:

Microscopic

Features:[1]

  • Proliferation of myoepithelium and epithelium (ductal cells) in mesenchymal stroma.
    • Cells in ducts = epithelial.
    • Cells not in ducts = myoepithelial.[2]
  • Mesenchymal stroma - important feature.
    • May be any of following: myxoid, mucochondroid, hyalinized, osseous, fatty.
      • Chondroid = specific for PA; can diagnose PA without an epithelial (ductal) component if chondroid is present.
      • Myxoid = not specific for PA.

Notes:

  • Mesenchymal stroma not required for diagnosis -- if >5% ducts.[2]
  • Complete excision is often elusive; stating "completely excised" on a surgical pathology report is unwise.
  • Look for, i.e. rule-out, poorly differentiated carcinoma: carcinoma ex pleomorphic adenoma.

Memory device: MEC = myoepithelium, epithelium, chondromyxoid stroma.

DDx:

Images

  • PA. (WC)

  • PA. (WC)

  • PA. (WC)

  • PA. (WC)

www:

IHC

  • S-100 +ve, SMA +ve, GFAP +ve.

See also

References

  1. ↑ 1.0 1.1 Thompson, Lester D. R. (2006). Head and Neck Pathology: A Volume in Foundations in Diagnostic Pathology Series (1st ed.). Churchill Livingstone. pp. 295. ISBN 978-0443069604.
  2. ↑ 2.0 2.1 Weinreb I. 10 January 2011.
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