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.
| 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.
