Diagnostic value of decreased expression of CD56 protein in papillary carcinoma of the thyroid gland

Background and aims: Precise pathological diagnosis is essential for optimal treatment of thyroid tumors. Ancillary diagnostic markers may be helpful in some cases. The purpose of this study was to compare and evaluate the diagnostic value of CD56, cytokeratin 19 (CK19), and galectin-3 immunohistochemical stainings in distinguishing between papillary carcinoma (PC) and other thyroid malignancies and benign lesions. Methods: The expressions of the three markers were evaluated in PC (n= 67), follicular carcinoma (FC, n= 23), medullary carcinoma (MC, n= 18), anaplastic carcinoma (AC, n= 4), follicular adenoma (FA, n= 15), and nodular hyperplasia (NH, n= 21). Results: Statistical analysis showed significantly different expressions of CD56, galectin-3, and CK19 in PC versus other lesions of the thyroid gland, with the exception of AC. Especially, the sensitivity and specificity of CD56 for diagnosing PC were 92.5% and 86.4%, respectively. The diagnostic specificity of CD56 was higher than that of galectin-3 or CK19 in differentiating PC from other lesions of the thyroid gland. However, its sensitivity was lower than that of galectin-3 or CK19. Conclusion: CD56 turns out to be a good negative marker for diagnosing PC. We suggest that immunohistochemical panels directed at the diagnosis of PC should include CD56 together with galectin-3 and CK19.