Background: The purpose of this study was to retrospectively evaluate technetium 99m tetrofosmin (Tc-TF) uptake in parathyroid adenomas and compare the results with their expression of multidrug resistance-mediated 170-kDa P-glycoprotein (Pgp).
Methods: Twenty patients with larger parathyroid adenomas (> 1.5 g) and the other 40 patients with smaller parathyroid adenomas (0.5-1.5 g) underwent early and delayed (10-minute and 2-hour) Tc-TF parathyroid imaging before operation. In this retrospective study, immunohistochemical analyses were performed on multiple nonconsecutive sections of the 40 parathyroid adenomas and 40 normal control specimens (20 normal parathyroid glands and 20 normal thyroid specimens) to detect Pgp expression.
Results: The Tc-TF parathyroid image accurately localized 17 larger and 16 smaller parathyroid adenomas, but not the remaining 3 larger and 4 smaller adenomas. The 17 larger and 16 smaller parathyroid adenomas with significant Tc-TF uptake on the delayed 2-hour parathyroid images revealed negative Pgp expression, but the 3 larger and 4 smaller adenomas without significant Tc-TF uptake, as well as 20 normal parathyroid glands and 20 normal thyroid specimens, revealed positive Pgp expression.
Conclusions: Not only the size of parathyroid adenomas, but Pgp expression also limited the sensitivity of Tc-TF parathyroid image to localize parathyroid adenomas before the operation.