Diagnostic utility of CD56 in differentiating papillary thyroid carcinoma from other lesions of thyroid

Abstract

Thyroid cancer is one of the most common malignant neoplasm worldwide. Among Indians, thyroid cancer constitutes 3.96% of total cancers. Papillary thyroid carcinoma (PTC) is a malignant epithelial tumor with distinctive nuclear features. PTC represents, about 85% of all malignant thyroid neoplasm. Though histopathological diagnosis is the gold standard for PTC diagnosis, pathologists usually face difficulty due to morphologic overlap between follicular neoplasms and PTC, especially the follicular variant of PTC. CD56 is a neuroendocrine marker and an antigen important for the follicular epithelium differentiation. Recent studies have reported low or absent expression of CD56 in PTC and its presence in normal thyroid tissue, benign thyroid lesions, and most follicular non-PTC tumors. This study aimed to assess the diagnostic utility of immunohistochemical marker, CD56 in distinguishing PTC from benign thyroid lesions and follicular neoplasms. This was a prospective and retrospective case control study conducted at department of Pathology of our institute. All 125 thyroidectomy specimens received during a study period from January 2017 to December 2019 were studied and any already established recurrent case of PTC was excluded. After routine histopathological examination, the expression of CD56 was studied and statistically analyzed. The difference between expression of CD56 antibody in differentiating PTC from other thyroid lesions was found to be statistically significant (p=<0.001). The sensitivity of CD56 was 94.6%, and its specificity was 97.7%. Thus, CD56 was found to be a valuable and sensitive biomarker even when used individually.