[ 18 F]Fluorocholine PET/CT false positive: foreign body reaction mimicking anaplastic glioma progression. A case report

Background Foreign body reaction in brain tissue is a very rare immune response that has not been well studied. Hemostatic material has been reported as a possible trigger of this response in other organs and could be detected by [ 18 F]fluorodeoxyglucose positron emission tomography/computerized tomography ([ 18 F]FDG PET/CT), but there is no reported experience about the role of [ 18 F]fluorocholine in this finding. [ 18 F]Fluorocholine has the potential to differentiate viable central nervous system tumors from other entities, so it is frequently used in the follow-up of neurosurgery patients. Case presentation A right frontoparietal neoplastic lesion was found in a young-aged patient with analgesic refractory headache. Surgical resection and postsurgical radiotherapy were performed, and the pathologist analysis turned out a cellular ependymoma with signs of anaplasia. In the follow-up, an magnetic resonance imaging (MRI) showed a suspicious lesion, so a [ 18 F]fluorocholine PET/CT was performed. Increased uptake was described in the right parietal region on the margin of the residual cystic lesion. The patient got a complete resection which was confirmed later by MRI. In the pathology analysis, a focally congestive cerebral parenchyma with a central histiocytic reaction to a foreign body area was described. Conclusions Following the experience of the current case report, [ 18 F]fluorocholine PET/CT could also show a false positive related to foreign body reaction. This entity should be considered to avoid unnecessary major surgery on our patients.