Incidental uptake of 18F-fluorocholine (FCH) in the head or in the neck of patients with prostate cancer
Positron emission tomography-computed tomography (PET/CT) with 18F-fluorocholine (FCH) is routinely performed in patients with prostate cancer. In this clinical context, foci of FCH uptake in the head or in the neck were considered as incidentalomas, except for those evocative of multiple bone metastases. In a total of 1181 FCH PET/CTs, 22 such foci in 21 patients have been reported (frequency=1.9% 95% confidence-interval: 1.1-2.6%) and their nature was characterised during follow-up in 10 patients.
In 8 patients the incidental focus corresponded to a benign tumour and to a malignant lesion in 2 other patients. The standard of truth was histology in four cases, correlative imaging with MRI in four cases, 99mTc-SestaMIBI scintigraphy, ultrasonography and biochemistry in one case and biochemistry including PTH assay in one case. The final diagnosis of benign tumours consisted in 3 pituitary adenomas, 2 meningiomas, 2 hyperfunctioning parathyroid glands and 1 thyroid adenoma.
To the best of our knowledge, FCH uptake by pituitary adenomas or hyperfunctioning parathyroid glands has never been described previously. We thus discuss whether there might be a future indication for FCH PET/CT when one such tumour is already known or suspected: to detect a residual or recurrent pituitary adenoma after surgery, to guide surgery or radiotherapy of a meningioma or to localise a hyperfunctioning parathyroid gland. In these potential indications, comparative studies with reference PET tracers or with 99mTc-sestaMIBI in case of hyperparathyroidism could be undertaken.