RAPID WASHOUT OF TECHNETIUM-99M-MIBI FROM A LARGE PARATHYROID ADENOMA

We report a case of rapid Tc-99m-methoxyisobutylisonitrile (MIBI) clearance from a parathyroid adenoma. A double-phase Tc-99m-MIBI parathyroid scintigraphy was performed on a 62-yr-old female evaluated for primary hyperparathyroidism. A large parathyroid adenoma was visualized caudal to the left robe of the thyroid gland with an unusually rapid washout of the tracer from tumor tissue. Histologic tissue examination confirmed the presence of a parathyroid adenoma and the absence of oxyphil cells. Care should be taken in interpretation of Tc-99m-MIBI parathyroid scintigrams because some adenomas can present a rapid release of the radiotracer in a double-phase study. Technetium-99m-MIBI retention could be related to the number of mitochondria-rich cells in parathyroid adenomas or to hyperplasia.