The Role of CD56, HBME-1, and CK19 Immunohistochemical Markers in the differential Diagnosing of Thyroid Neoplasms.

Background: The diagnosis of thyroid neoplasms is steadily increasing due to the widespread use of sensitive diagnostic techniques. While histopathologic evaluation using Hematoxylin and Eosin (H&E) staining is considered the "gold standard," it often faces challenges due to morphological overlap between benign and malignant follicular patterned lesions. This led to diagnostic uncertainties, underscoring the need for Immunohistochemistry (IHC) as a valuable adjunct. This study aims to evaluate the expression of IHC markers, Hector Battifora Mesothelial Cell-1 (HBME-1), Cluster of Differentiate (CD56 also known as Neural Cell Adhesion Molecule) and Cytokeratin-19 (CK19), in follicular patterned neoplasms of thyroid to aid in the diagnosis of malignant thyroid neoplasms.

Methodology: The study was a descriptive analysis and it included 60 thyroidectomy specimens diagnosed as neoplastic by histopathology were studied after satisfying the inclusion and exclusion criteria. The IHC results were interpreted semi-quantitatively. Statistical analysis was performed using Chi-square test and Fisher's-exact tests. P-value of <0.05 was considered as significant. Sensitivity and specificity for each marker and their combination in diagnosis were calculated.

Results: Among the sixty cases, 31.67% were benign neoplasms, and 68.33% were malignant. Loss of CD56 expression was noted in 75.68% of malignant cases. The specificity of CD56, HBME-1, and CK19 in identifying malignant neoplasms was 84.21%, 84.21%, and 89.47%, respectively. The accuracy of CD56 and CK19 in diagnosing follicular variant papillary thyroid carcinoma (FVPTC) from follicular adenoma (FA) was 79.31% and 93.10%, respectively. The specificity of CK19 in distinguishing FVPTC from FA was 89.47%. The specificity of CD56, CK19, and HBME-1 in diagnosing follicular thyroid carcinoma (FTC) from FA was 84.21%, 85%, and 84.21%, respectively.

Conclusion: Our study highlights the diagnostic utility of CD56, CK19, and HBME-1 in thyroid neoplasms incorporating these markers into routine diagnostic panels can significantly enhance the accuracy and reliability of thyroid malignancy assessments.