Incidental Findings on F-Fluorocholine PET/CT for Parathyroid Imaging.

F-choline positron emission tomography/computed tomography (PET/CT) is an upcoming imaging technique for the localization of hyperfunctioning parathyroid glands. However, F-choline is a nonspecific tracer that also accumulates in malignancies, inflammatory lesions, and several other benign abnormalities. The aim of this study was to determine the occurrence and relevance of incidental findings on F-choline PET/CT for parathyroid localization.   F-choline PET/CTs performed in our center for parathyroid localization from 2015 to 2019 were reviewed. Abnormal uptake of F-choline, with or without anatomical substrate on the co-registered low-dose CT and also incidental findings on CT without increased F-choline uptake were recorded. Each finding was correlated with follow-up data from the electronic medical records.  A total of 388 F-choline PET/CTs were reviewed, with 247 incidental findings detected in 226 patients (58%): 82 F-choline positive findings with corresponding pathology on CT, 16 without CT substrate, and 149 F-choline negative abnormalities on CT. Malignant lesions were detected in 10/388 patients (2.6%). Of all 98 detected F-choline positive lesions, 15 were malignant (15.3%), concerning 4 metastases and 11 primary malignancies: breast carcinoma (  = 7), lung carcinoma (  = 2), thyroid carcinoma (  = 1), and skin melanoma (  = 1).  Clinically relevant incidental findings were observed in a substantial number of patients. In 15.3% of the incidental F-choline positive findings, the lesions were malignant. These data contribute to better knowledge of F-choline distribution, enhance interpretation of F-choline PET/CT, and guide follow-up of incidental findings. Attention should especially be paid to breast lesions in this particular patient group with hyperparathyroidism in which women are typically over-represented.