Giant cell tumor

• Cannot tell based on appearance if benign or malignant and also difficult on histology
• Most surgeons consider benign unless they recur after curettage and packing

Discriminators (applies to long bones only not flat bones)

• Epiphyses must be closed
• Must abut the articular surface
  • Should be flush against the articular surface of the joint
• Must be well defined with a nonsclerotic margin
  • Sharply defined zone of transition
• Must be eccentric

If any one of these is untrue, can rule out GCT with 95% reliability