TROP-2 Immunohistochemistry: The Evaluation of TROP-2 in the Diagnosis of Thyroid Neoplasms

staining in other variants. 3Given these findings, TROP-2 could serve as a valuable immunohistochemical marker in differentiating follicular-patterned thyroid neoplasms and distinguishing malignant from benign lesions.The diagnosis of thyroid tumors primarily relies on hematoxylin and eosin (H&E) stained sections, but in challenging cases, IHC markers such as HBME-1, Galectin-3, CK19, CD56, and TROP-2 help refine the diagnosis.While HBME-1 and Galectin-3 are well-established markers for PTC, their specificity and sensitivity vary, necessitating the exploration of additional markers such as TROP-2. 4,5Its membranous and cytoplasmic staining patterns, along with its distinct expression in PTC subtypes, make it a promising candidate for enhancing diagnostic precision in thyroid histopathology. IntroductIonThyroid tumors are a wide spectrum of lesions, ranging from benign nodules to highly aggressive carcinomas.According to the latest GLOBOCAN 2022 data from the International Agency for Research on Cancer (IARC), thyroid cancer ranked 7th globally in incidence, with 821,214 new cases reported and an agestandardized incidence rate (ASR) of 9.1 per 100,000 people. 1 Among various immunohistochemical markers, trophoblast cellsurface antigen-2 (TROP-2) has emerged as a potential diagnostic and prognostic biomarker in epithelial malignancies.TROP-2, a transmembrane glycoprotein encoded by the TACSTD2 gene, plays a key role in cell proliferation, adhesion, migration, invasion, and metastasis. 2 Initially identified in trophoblastic tissues, TROP-2 has been found to be overexpressed in various human carcinomas, including colorectal, gastric, pancreatic adenocarcinoma, oral squamous cell carcinoma, nonsmall cell lung carcinoma, endometrial, and ovarian carcinoma, with limited expression in normal tissues.Its overexpression has been associated with poor prognosis and aggressive tumor behavior.While TROP-2 has been extensively studied in several malignancies, its role in thyroid neoplasms remains relatively unexplored.Recent studies suggest that TROP-2 expression is significantly higher in papillary thyroid carcinoma (PTC) than in benign thyroid lesions, indicating its potential as a diagnostic marker.The pattern and intensity of TROP-2 staining may vary among different histological variants of PTC, with diffuse positivity in FVPTC and focal membranous 1-