Differences in histopathologic features and diagnostic performance of 99mTc-methoxy-isobutyl-isonitrol single photon emission tomography-CT and 18F-fluorocholine positron emission tomography-CT in primary hyperparathyroidism.

Background: Primary hyperparathyroidism is a common endocrine disorder. Accurate preoperative localization is crucial for the success of minimally invasive parathyroidectomy. Although ⁹⁹mTc-methoxy-isobutyl-isonitrol single photon emission computed tomography-computed tomography remains the gold standard imaging technique, its diagnostic performance can be limited in certain clinical scenarios. In recent years, ¹⁸F-fluorocholine positron emission tomography-computed tomography has emerged as a promising alternative, especially in cases where first-line imaging results are inconclusive or negative. However, the mechanisms contributing to its superior diagnostic performance remain incompletely understood. The study aims to assess the diagnostic accuracy of ¹⁸F-fluorocholine positron emission tomography-computed tomography in patients with negative or discordant ⁹⁹mTc-methoxy-isobutyl-isonitrol single photon emission computed tomography-computed tomography results and to evaluate the biochemical and histopathologic characteristics of hyperfunctioning glands detected by each imaging modalities.

Methods: A retrospective study was performed of 245 primary hyperparathyroidism patients who underwent parathyroid surgery between January 2021 and April 2024. Imaging findings were correlated with biochemical data, histopathology, and surgical outcomes. Semiquantitative positron emission tomography parameters were analyzed and statistical comparisons were made regarding gland size, weight, cellular composition, and growth patterns.

Results: ¹⁸F-Fluorocholine positron emission tomography-computed tomography presented a sensitivity of 93.1% and a diagnostic accuracy of 78.8%. This imaging modality identified smaller glands and was more frequently associated with chief-cell predominance. ⁹⁹mTc-methoxy-isobutyl-isonitrol single photon emission computed tomography-computed tomography demonstrated a sensitivity of 70.4% and an accuracy of 60.7%, with higher radiotracer uptake observed in oxyphilic and oncocytic adenomas. The maximum standardized uptake value correlated with parathyroid hormone levels and gland size but not with cellular composition or growth pattern.

Conclusion: ¹⁸F-fluorocholine positron emission tomography-computed tomography demonstrates high diagnostic performance in lesion localization, particularly in patients with negative or inconclusive first-line imaging. These findings suggest that radiotracer uptake may be influenced by biochemical and morphologic features, although further studies are warranted to clarify these mechanisms.