Surgical Pathology Criteria

Parachordoma

Differential Diagnosis

Chordoma Parachordoma
Occurs on craniospinal axis Non-axial location
CK7 and 34BE12 positive CK7 and 34BE12 negative
No collagen IV around nests Collagen IV around nests
  • Both are S100 and CK8/18 positive.
  • Mestastic chordoma must be ruled out.
  • Ectopic chordoma is controversial and requires immunohistology features above.
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    Myxoid Chondrosarcoma Parachordoma
    Predominantly long chains of cells Predominantly nests and cords of cells
    Uniformly small cells Small and large cells
    EMA and keratin rarely positive EMA and keratin uniformly positive
    S100 infrequent, patchy S100 consistent, uniform
    Stroma purely myxoid Stroma myxoid and hyalinized
    Alcian blue hyaluronidase resistant Alcian blue hyaluronidase sensitive
    t(9;22) in 75% of cases t(9;22) not seen

     

    Chondroid Syringoma of Skin Parachordoma
    Actin positive component Actin negative
    No large vacuolated cells Large vacuolated cells at least focally
    Both are S100 and keratin positive

     

    Chondroid Lipoma Parachordoma
    Contains mature fat No fat integral to lesion
    EMA negative EMA positive
    Keratin variable Keratin positive
    Both are S100 positive

     

    Myoepithelioma Parachordoma
    Actin positive Actin negative
    May form ducts No true ducts
    Both are keratin and S100 positive.

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