Endocrine Abstracts

Introduction: CD56 (neural cell adhesion molecule/NKH1/LEU19 and LEU7/NHK-1) is an antigen related to follicular epithelium differentiation.

Materials and methods: We evaluated the expression of CD56 protein in normal follicular thyroid tissue, 15 non-neoplastic thyroid lesions (nodular hyperplasia–NH, Graves–Basedow disease (GB) and chronic lymphocytic/Hashimoto is thyroiditis (HT) and 38 thyroid neoplasias derived from follicular cells (25 PTC and 13 follicular neoplasias (five follicular adenomas (FA), two FA with Hurthle cells, two follicular carcinomas (FC), 1 Hurthle cell carcinoma (HCC) and three follicular tumors with uncertain malignant potential (FT-UMP), in our attempt to appreciate the value of this marker in differentiating PTC (including its follicular variant (FV)) from other follicular lesions/neoplasias. The IHC reactions were carried out on sections stained with the anti-CD56 antibody (clone 1B6), dilution 1:100, using the EnVision+Dual Link System-HRP (visualization with DAB). For the statistical analysis, the χ² test was used, values ≤0.05 being considered statistically significant.

Results: We noted CD56 expression in 28.95% of follicular tumors and 15.79% of PTC; CD56 immunoexpression differentiated PTC from non-neoplastic benign lesions (NH, GB and HT) (P=0.017; χ² test), as well as from follicular neoplasias (FC and HCC) (P=0.0455). The results were also significant when we compared CD56 expression in PTC with the one in FA, NH and HT (P=0.0124) and PTC–FV with non-malignant lesions (FA+NH+HT) (P=0.0080) or with non-tumor thyroid lesions (NH+HT+GB) (P=9096655E-05), respectively. We did not observe significant differences in the expression of CD56 when differentiating PTC–FV from classical PTC (P=0.4362). Solid cell nests were the only lesions in the thyroid gland with negative CD56 immunophenotype, similar to PTC.

Conclusions: CD56 proves to be a useful marker in the diagnosis of PTC, including PTC–FV and microcarcinoma; the absence of CD56 expression in PTC–FV can be a useful biomarker in differentiating PTC–FV from other thyroid nodules with follicular pattern.