TROP2 IMMUNOEXPRESSION IN THYROID NEOPLASMS: DIAGNOSTIC UTILITY AND HISTOPATHOLOGICAL CORRELATION

Abstract

Background: Thyroid neoplasms, particularly follicular-patterned lesions, show considerable morphological overlap, creating diagnostic challenges. Trophoblast cell surface antigen 2 (TROP2), a transmembrane glycoprotein, has demonstrated potential diagnostic utility in papillary thyroid carcinoma (PTC). This study evaluated TROP2 immunoexpression across malignant and borderline thyroid neoplasms and its association with histopathological subtypes in an Indian cohort. Materials and Methods: A cross-sectional study was conducted on 70 malignant and borderline thyroid neoplasms. Representative tissue sections were subjected to TROP2 immunohistochemistry. Membranous staining in ≥5% of tumor cells was considered positive. Diagnostic performance was evaluated using PTC as the target category. Results: Of the 70 cases, 58 (82.9%) were PTC, 3 (4.3%) noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), 5 (7.1%) follicular thyroid carcinoma, 3 (4.3%) medullary thyroid carcinoma, and 1 (1.4%) anaplastic thyroid carcinoma. TROP2 positivity was observed in 55/58 (94.8%) PTCs, including 21/23 (91.3%) follicular variant PTCs. All NIFTP and non-papillary thyroid carcinomas were negative. TROP2 expression was significantly associated with histopathological diagnosis (P < 0.0001). Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for identifying PTC were 94.8%, 100%, 100%, 80.0%, and 95.7%, respectively. Conclusion: TROP2 demonstrates predominantly positive membranous expression in PTC and may serve as a useful adjunctive immunohistochemical marker in the evaluation of diagnostically challenging thyroid lesions, particularly follicular-patterned neoplasms.