Parachordoma

Definition

Neoplasm of small to large, frequently vacuolated cells set in a hyalinized matrix, similar in appearance to a chordoma but arising away from the craniospinal axis

Cords and nests of cells
- May form whorls
- May form pseudoglands
- Hyalinized stroma
Predominantly large cells with eosinophilic cytoplasm
- Occasional physalliferous cells
  - Very large cells with vacuolated cytoplasm
- Merge with spindled or small round cells
- Vesicular to pyknotic nuclei
Positive for S100 and CK 8/18 (Cam5.2)
No mitotic figures, necrosis or vascular invasion
Circumscribed, not encapsulated
Non-axial location
- Mestastatic chordoma must be ruled out

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting:: February 3, 2007