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

We report a case of rapid Tc-99m-methoxyisobutylisonitrile (MIBI) clea rance from a parathyroid adenoma. A double-phase Tc-99m-MIBI parathyro id scintigraphy was performed on a 62-yr-old female evaluated for prim ary hyperparathyroidism. A large parathyroid adenoma was visualized ca udal to the left robe of the thyroid gland with an unusually rapid was hout of the tracer from tumor tissue. Histologic tissue examination co nfirmed the presence of a parathyroid adenoma and the absence of oxyph il cells. Care should be taken in interpretation of Tc-99m-MIBI parath yroid scintigrams because some adenomas can present a rapid release of the radiotracer in a double-phase study. Technetium-99m-MIBI retentio n could be related to the number of mitochondria-rich cells in parathy roid adenomas or to hyperplasia.