The potential diagnostic value of TROP-2 expression in papillary thyroid carcinoma, benign thyroid lesions, and borderline thyroid lesions: immunohistochemical study

Abstract

Background The diagnosis of the papillary thyroid carcinoma (PTC) depends on characteristic histopathological features. However, there may be cases with inconsistent features, necessitating the use of immunohistochemical markers. Aim To investigate the value of TROP-2 expression in the diagnosis of PTC and its differentiation from benign thyroid lesions and to evaluate its expression in the newly introduced WHO borderline thyroid lesions. Patients and methods The immunohistochemical expression of TROP-2 was analyzed in 55 selected cases of surgically removed thyroid lesions, which included PTC (30), benign thyroid lesions (16), and borderline thyroid lesions (nine), namely, noninvasive follicular tumor with papillary nuclear features and well-differentiated tumors of uncertain malignant potential. Results TROP-2 positivity and combined score were significantly higher in PTC than in benign thyroid nodules with TROP-2 positivity, showing 86.7% sensitivity and 93.8% specificity. TROP-2 positivity disclosed significant differences between follicular variant papillary thyroid carcinoma (FVPTC) and benign follicular patterned nodules (BFPN), with sensitivity and specificity of 70 and 80%, respectively, and between borderline lesions and BFPN, with sensitivity and specificity of 55.6 and 73.6%, respectively. TROP-2 combined score cutoff points of more than or equal to 3, more than or equal to 2, and more than or equal to 2 can significantly differentiate total PTC versus benign lesions, FVPTC versus BFPN, and borderline lesions versus BFPN, respectively, with specificity mounting to 100%, whereas no significant difference was found between FVPTC and borderline lesions with respect to TROP-2 positivity and combined score. Conclusion TROP-2 is a potential valuable marker that can aid in diagnosis of PTC and differentiating it from its benign mimics with high sensitivity and specificity. The immunohistochemical profile of borderline thyroid lesions (well-differentiated tumors of uncertain malignant potential and noninvasive follicular tumor with papillary nuclear features) for TROP-2 suggests the possibility of their malignant precursor nature. Hence, close strict follow-up for borderline cases may be advisable.