Introduction: Following intralesional resection of giant cell tumour local recurrence happens in up to 40% depending on type of treatment. Common plain radiography or Magnetic resonance tomography (MRI) often has the problem not to discriminate between scar and recurrent tumour.

Materials and Methods: In 19 patients with giant cell tumour dynamic PET using F18-Fluordeoxyglucose (FDG) for estimation of FDG turnover was carried out. PET was performed before surgery and as follow up. In case of evidence in x-ray or MRI of recurrent giant cell tumour PET was performed again. results of histologic evaluation after reoperation then were compared to results of PET.

Results: All giant cell tumours showed a specific PET pattern with a very high standard uptake value (SUV) of 4.8 in median. In one case pulmonary metastases could be found. In follow up after surgery this value dropped to 0.3. Recurrence was suspected in the follow up in 5 patients by MRI or plain radiography. In all these patients PET could show an elevated SUV above 4.0. In these 5 patients surgery was performed and recurrence could be proven by histology. In one patient MRI was negative but PET showed a SUV of 5.2 indicating re-recurrent tumour which could be demonstrated by histology.

Conclusion: We conclude that PET is a very helpful tool not only in the first line diagnosis of giant cell tumour but also in diagnosis of metastatic disease and especially for detection of recurrent tumour.