Expression of Immunohistochemical Markers (CD56 and P63) in Various Non-Neoplastic and Neoplastic Lesions of Thyroid Gland.

Introduction: Thyroid disorders are very common all over India, more so in Kerala. Although definite histologic criteria exist for diagnosing various thyroid lesions, there is an overlap of many nuclear and cytoplasmic features like nuclear atypia, enlargement etc., between both non-neoplastic and neoplastic lesions. This sometimes leads to a diagnostic dilemma in differentiating these lesions. CD56 is expressed by many tissues in the body including normal thyroid follicular epithelium, this expressivity being absent or reduced in Papillary Thyroid Carcinoma (PTC). Normal thyroid follicular cells do not express p63. Aberrant expression of p63 on thyroid epithelium is thus a marker of proliferation and tumourigenesis. Aim: To assess the expression of CD56 and p63 in various nonneoplastic and neoplastic thyroid lesions and to calculate the percentage of positivity and negativity in these lesions. Materials and Methods: This was a prospective study of 100 thyroidectomy specimens submitted to the Department of Pathology, Govt. TD Medical College, Alappuzha from January 2016 to June 2017. H&E stained sections of these specimens were studied and Immunohistochemical (IHC) staining with CD56 and p63 markers was performed on all and their expressions, positive or negative, were evaluated and expressed as percentage values. Results: Out of 100 thyroidectomy specimens studied, total number of non-neoplastic cases was 58 and neoplastic lesions (benign and malignant) were 42. The most common nonneoplastic lesion was lymphocytic thyroiditis (39/58). Most common malignant thyroid neoplasm was PTC (35/42). CD56 showed membranous positivity in 53/58 (91.4%) non-neoplastic lesions and only 4/42 (9.5%) neoplastic lesions. Nuclear positivity for p63 was seen in only a small proportion (18/100, i.e., 18%) of all lesions. Conclusion: Significance of this study lies in the fact that CD56 is expressed in most non-neoplastic lesions of thyroid and is found negative in thyroid malignancies. The p63 even though considered to be a proliferation marker is negative in most of nonneoplastic as well as neoplastic lesions in the present study. [ABSTRACT FROM AUTHOR]