18 F-FET PET Pitfall in Pituitary Imaging: False-positive Uptake Due to Neurosarcoidosis.
Chloé Merino, Camille Sergeant, Alexandre Vasiljevic et al.
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Case in brief
A 38-year-old man with previously treated pulmonary sarcoidosis underwent pituitary imaging. MRI showed a left-sided pituitary neuroendocrine tumor (PitNET), whereas 18F-FET PET/CT showed uptake on both sides, with greater activity on the right. Histopathology identified a corticotroph-type PitNET on the left and noncaseating granulomas consistent with sarcoidosis on the right. The discordant PET finding was therefore attributable to neurosarcoidosis rather than tumor on the right.
What made this case unusual
Sarcoid granulomas produced greater 18F-FET uptake than the contralateral, histologically confirmed PitNET, creating a false-positive appearance for tumor involvement.
Diagnostic / clinical pearl
Discordant pituitary 18F-FET uptake, particularly when it does not match MRI findings, may reflect neurosarcoidosis; correlate imaging with clinical history and histopathology.