Significance of Insulin-Like Growth Factor II Mrna-Binding Protein 3 (IMP3) Expression in Selected Thyroid Lesions

Background: Differentiation of benign from malignant follicular thyroid lesions remains difficult and the ability of molecular markers to differentiate between them still unclear. The aim of this study was to evaluate the usefulness of IMP3 expression to distinguish benign from malignant thyroid lesions. Methods: This is a retrospective study upon selected 57 thyroid lesions designated as; 7 cases of Hashimoto thyroiditis (HT), 10 cases of hyperplastic nodules (HN), 15 cases of follicular thyroid adenoma (FTA), 13 cases of  conventional papillary thyroid carcinoma (PTC), 6 cases of follicular variant of papillary thyroid carcinoma (FV-PTC), and 6 cases of follicular thyroid carcinoma (FTC). Immunohistochemistry was applied on formalin-fixed, paraffin-embeded tissue blocks using IMP3. clinicopathological data were reviewed from patients' pathological reports and correlated with IMP3 expression. Results: IMP3 positivity was seen in1/7 cases (14.3%) of HT, 2/10 cases (20%) of HN, 4/15 cases (26.7%) of FTA, 12/13 cases of PTC, and in all (100%) FV-PTC & FTC cases. IMP3 staining was significantly increased from normal thyroid tissue up to malignant tumors (P<0.01). IMP3 showed 96% sensitivity and 78.1% specificity for malignant tumors. IMP3 expression was positively correlated with grade and tumor size in malignant cases (P<0.05). No significant correlation was found in IMP3 expression with patient age, sex, capsular invasion, lymphatic/vascular invasion, lymph node metastasis, distant metastasis and TNM stage.  Conclusions: IMP3 is a potential diagnostic marker for thyroid cancer and can be a promising marker for distinguishing benign from malignant follicular patterned thyroid lesions.