Diagnostic Significance of Trophoblast Cell Surface Antigen-2 Expression in Benign and Malignant Thyroid Lesions

Introduction Trophoblast cell surface antigen-2 (TROP-2), a transmembrane glycoprotein associated with trophoblast cells, is found to have a potential role in the proliferation of cancer cells and their ability to progress, invade and survive. An immunohistochemical study of TROP-2 can be helpful to differentiate benign and malignant thyroid lesions and guide clinical management. The study aimed to evaluate the diagnostic significance of TROP-2 expression in thyroid lesions. Materials and methods This cross-sectional study was conducted in a tertiary care teaching hospital, which included 44 cases of benign and malignant thyroid lesions. Tissue sections (4 µm thick) were obtained from paraffin-embedded blocks after deparaffinization and antigen retrieval in citrate buffer. The samples were tested for TROP-2 expression by immunohistochemistry. Collected data were entered in Microsoft Excel (Microsoft Corporation, Redmond, WA), and statistical analysis was performed using Statistical Packages for Social Sciences (SPSS) Version 23.0 (IBM Corp., Armonk, NY). A p-value less than 0.05 was considered statistically significant. Results The mean age of the study population was 42.84, and the range was from 16 years to 75 years. Among them, 37 subjects (84.09%) were female. On histopathological examination, 17 cases (38.64%) were diagnosed as benign thyroid lesions, 26 cases (59.09%) were of malignant thyroid lesions, and one case was diagnosed as a borderline lesion (non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)). The proportion of TROP-2 positivity was significantly different between benign and malignant thyroid lesions, and between papillary thyroid carcinoma (PTC) and non-PTC malignant lesions. The sensitivity of TROP-2 IHC testing was found to be 69.23% for diagnosing malignant thyroid lesions and 78.26% for diagnosing PTC cases. The specificity and positive predictive value in both conditions were observed to be 100%. The proportion of TROP-2 positivity did not significantly differ among the different tumour stages and lymph node status groups. Conclusion TROP-2 as a diagnostic marker was observed to have high specificity, which indicates that it has a promising role as an adjunct diagnostic method to the currently available methods. However, TROP-2's sensitivity is found to be moderate, which indicates that this marker cannot be used as a standalone diagnostic tool but rather in conjunction with other markers and histopathological examination.