CD56 and High Molecular Weight Cytokeratin as Diagnostic Markers of Papillary Thyroid Carcinoma

ABSTRACT

BACKGROUND: The incidence of papillary thyroid carcinoma (PTC) has been increasing recently and a precise diagnosis is essential for optimal treatment. Ancillary immunohistochemical stains are important for diagnosing some difficult cases. METHODS: The dignostic value of CD56, high molecular weight cytokeratin (HMCK), galectin-3 (GAL3), and cytokeratin 19 (CK19) were evaluated to distinguish PTC from other benign thyroid lesions (BTL). We studied 23 cases of papillary thyroid overt carcinomas, 57 papillary thyroid microcarcinomas, five follicular adenomas, five cases of Hashimoto's thyroiditis, and 12 nodular hyperplasias. RESULTS: The statistical analysis showed significantly different expressions of CD56, HMCK, GAL3, and CK19 in PTC vs other BTL. The diagnostic specificity of HMCK and CD56 (90.9% and 72.7%, respectively) was higher than that of GAL3 and CK19 (50.0% and 36.4%, respectively). However, the sensitivity of HMCK and CD56 detection (92.5% and 95.0%, respectively) was lower than that of GAL3 and CK19 (98.8% and 100.0%, respectively). The combined use of CD56, HMCK, GAL3, and CK19 showed 87.5% sensitivity, 100.0% specificity, and 100.0% positive predictive value in differentiating PTC from other BTL. CONCLUSIONS: Although the differential diagnosis of thyroid follicular lesions are based on histological and cytomorphological criteria, CD56 and HMCK might be useful markers for diagnosing PTC.