The uptake mechanism of SPECT-CT in hyperfunctioning glands appears to be associated with mitochondrial uptake in oxyphilic cells-rich. The uptake mechanism of 18F-choline PET/CT is suggested to be associated with the production and secretion of PTH, which mainly occurs in chief cells. The aim was to compare the histopathological features, specifically the predominant cell type and growth pattern of hyperfunctioning parathyroid glands that uptake on choline PET/CT with those parathyroid that uptake on SPECT-CT.

Two groups of 40 patients with PHPT undergoing parathyroidectomy between 2021-2022 were compared. The groups were established based on preoperative parathyroid imaging. 18F-choline PET/CT was performed when other localization modalities were negative or discordant. Preoperative analytical parameters and postoperative histopathologic features were evaluated. The total absolute amounts of cells were calculated by multiplying the volume of the parathyroid lesion by the percentage of each type of cell.

Preliminary results did not reveal differences in preoperative analytical parameters. Concerning histopathological features, median gland weight was lower in choline subgroup (645 mg [64-8300] vs. 1246.3 [90-7530], p=0.01). Total absolute amounts of oxyphilic cells were lower in choline group (122 vs. 170.3, p=0.03). In choline group, a positive correlation was observed between SUVmax and the proportion of principal cells, while the correlation with proportion of water cells was negative.

The uptake mechanisms of SPECT-CT and 18F-choline PET seem to differ. According to our results, we observed differences in terms of the predominant cell type of hyperfunctioning glands, with the significant difference in absolute oxyphilic cells between the two groups.