Difference between revisions of "Pleomorphic adenoma"

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{{ Infobox diagnosis
| Name      = {{PAGENAME}}
| Image      = Pleomorphic_adenoma_%281%29_parotid_gland.jpg
| Width      =
| Caption    = Pleomorphic adenoma. [[H&E stain]].
| Micro      = proliferation of myoepithelium and epithelium in mesenchymal stroma; cells in ducts = epithelial, cells not in ducts = myoepithelial, mesenchymal stroma = [[chondromyxoid stroma|Chondroid]] stroma (specific), or mucochondroid, hyalinized, osseous, fatty, myxoid
| Subtypes  =
| LMDDx      = [[myoepithelioma]], [[carcinoma ex pleomorphic adenoma]], [[epithelial-myoepithelial carcinoma]]
| Stains    =
| IHC        = S-100 +ve, SMA +ve, GFAP +ve
| EM        =
| Molecular  =
| IF        =
| Gross      =
| Grossing  =
| Site      = [[salivary gland]] - usu. parotid gland, other sites
| Assdx      =
| Syndromes  =
| Clinicalhx =
| Signs      = mass lesion
| Symptoms  =
| Prevalence = common
| Bloodwork  =
| Rads      =
| Endoscopy  =
| Prognosis  = benign
| Other      =
| ClinDDx    = other [[salivary gland]] tumours
}}
'''Pleomorphic adenoma''', abbreviated '''PA''', is a very common benign [[salivary gland]] tumour.
'''Pleomorphic adenoma''', abbreviated '''PA''', is a very common benign [[salivary gland]] tumour.


Revision as of 15:36, 10 November 2013

Pleomorphic adenoma
Diagnosis in short

Pleomorphic adenoma. H&E stain.
LM proliferation of myoepithelium and epithelium in mesenchymal stroma; cells in ducts = epithelial, cells not in ducts = myoepithelial, mesenchymal stroma = Chondroid stroma (specific), or mucochondroid, hyalinized, osseous, fatty, myxoid
LM DDx myoepithelioma, carcinoma ex pleomorphic adenoma, epithelial-myoepithelial carcinoma
IHC S-100 +ve, SMA +ve, GFAP +ve
Site salivary gland - usu. parotid gland, other sites
Signs mass lesion
Prevalence common
Prognosis benign
Clin. DDx other salivary gland tumours

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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