The Positive Effect of Adenoma Weight and Oxyphil Cell Content on Preoperative Localization with 99mTc-sestamibi Scanning for Primary Hyperparathyroidism

Background: Although the sensitivity of sestamibi scanning (MIBI) is high in patients with solitary parathyroid adenomas, negative sestamibi scan results are inevitable. The exact mechanism of visualization of abnormal and hyperfunctioning parathyroid tissue is not yet clear. The aims of this clinical study were (1) to evaluate positive and negative sestamibi scan results with regard to adenoma weight and oxyphil cell content and (2) to compare the effects of adenoma weight and oxyphil cell content on the results of sestamibi scanning.

Patients: The patients were divided in 2 groups according to their sestamibi scan results. Group 1 consisted of 27 patients with positive sestamibi scan results, and group 2 consisted of 20 patients with negative sestamibi scan results. Parathyroid adenoma weight and oxyphil cell content were determined in all patients.

Results: The weight and oxyphil cell content of the parathyroid adenomas in the patients of group 1 were significantly higher than those in the patients of group 2 (P = .001). An adenoma weight >600 mg and an oxyphil cell content >20% increased the rate of obtaining a positive sestamibi scan result 10- and 4-fold, respectively.

Conclusions: Both adenoma weight and oxyphil cell content were found to significantly correlate with positive sestamibi scan results. In patients with high-weight adenomas, adenoma weight was the most significant factor in obtaining positive MIBI scan results, whereas in patients with low adenoma weights, high oxyphil cell content was the most significant factor in obtaining positive MIBI scan results.