^99mTc-MIBI Imaging in the Presurgical Characterization of Thyroid Follicular Neoplasms: Relationship to Multidrug Resistance Protein Expression

Abstract

Recently, thyroid 99m Tc-methoxyisobutylisonitrile ( 99m Tc-MIBI) scintiscanning has been proposed in an attempt to preoperatively identify thyroid malignancies, but discrepant results have been reported for oncocytic lesions. The aim of this study was to investigate the usefulness of visual and semiquantitative analyses of 99m Tc-MIBI scintigraphy for preoperatively characterizing thyroid nodules with indeterminate cytologic diagnoses, segregating in advance nononcocytic variants from those that are oncocytic. This study also aimed to analyze the relationship between 99m Tc-MIBI images and P-glycoprotein (P-gp)/multidrug resistance-associated protein-1 (MRP1) immunohistochemical expression. Methods: Fifty-one consecutive patients with cold thyroid nodules cytologically diagnosed as nononcocytic or oncocytic follicular neoplasm were prospectively studied. Visual and semiquantitative 99m Tc-MIBI scanning was performed and the diagnoses of the lesions were histologically proven by subsequent thyroidectomy. Immunohistochemical evaluation of P-gp and MRP1 was also performed on surgical samples. Results: Visual and semiquantitative 99m Tc-MIBI scintiscans showed a low specificity in preoperatively discriminating malignant oncocytic lesions. In nononcocytic nodules, the semiquantitative method was more accurate than the visual (94.44% and 77.78%, respectively). P-gp protein expression was negative in all thyroid lesions, whereas apical plasma membrane MRP1 expression was found in 78% of the lesions with a negative 99m Tc-MIBI retention index, compared with 11% of lesions with a positive retention index, correlating most strongly with a negative 99m Tc-MIBI RI in those cases with strong MRP1 apical expression. Conclusion: Semiquantitative 99m Tc-MIBI scintigraphy is an adjunctive method to predict preoperatively the malignant behavior of nononcocytic follicular thyroid nodules indeterminate at fine-needle aspiration biopsy, with a potential impact on the definition of their clinical management. Moreover, the good correlation found between immunohistochemical apical expression of MRP1 and the scintigraphic findings supports the 99m Tc-MIBI results and provides tissue information on the molecular mechanisms responsible for 99m Tc-MIBI images in thyroid lesions.

Microwave Ablation of Symptomatic Benign Thyroid Nodules: Energy Requirement per ml Volume Reduction

“…All patients underwent 99 m Tc-pertechnetate scintigraphy. In the case of "cold" nodules, 99 m Tc-MIBI scintigraphy and fine-needle aspiration biopsy were performed to exclude signs of malignancy [12,13].…”

DIAGNOSIS OF ENDOCRINE DISEASE: High-yield thyroid fine-needle aspiration cytology: an update focused on ancillary techniques improving its accuracy

“…Recent AACE, AME, and ETA guidelines recognize such differences and suggest the use of thyroid scans taking into consideration the iodine supply in different geographical areas. Tc-MIBI, due to their peculiar molecular mechanism of 99m Tc-MIBI washout from the cells (63). In summary, due to its low specificity, 99m Tc-MIBI scan cannot be recommended as a first-line investigation.…”

Thyroid nodules with indeterminate cytology: prospective comparison between 18F-FDG-PET/CT, multiparametric neck ultrasonography, 99mTc-MIBI scintigraphy and histology

“…99m Tc-MIBI scan may be useful in the pre-surgical evaluation of thyroid nodules with undetermined cytology, and it has proved to be a specific tracer in identifying malignancy in non-oncocytic follicular lesions. However, it has not proved specific enough to distinguish benign oncocytic follicular lesions from malignant ones (10). 18 F-FDG PET/CT seems to be helpful in defining the nature of indeterminate nodules and has been reported to have a very high NPV (11,12,13,14,15,16,17).…”