Role of Immunohistochemistry in Diagnosis of Papillary Thyroid Carcinoma: The Use of Ck19, CD56, P63 and CD117

Objective: Papillary thyroid carcinoma (PTC) is the most frequent histologic type of all thyroid malignancies. The presence of characteristic nuclear changes focally in a thyroid lesion may cause diagnostic dilemma. Immunohistochemistry may be helpful in the diagnosis of PTC yet not conclusive. The aim of this study is to test the applicability immunohistochemical markers; CK19, P63, CD56 and CD117 in distinguishing PTC from other follicular thyroid. Methods: Fifty nine cases of unequivocal diagnosis were selected to be rolled in our study; 24 papillary carcinoma cases and 35 cases representing other follicular throid lesions. Immunohistological studies include CK19, P63, CD56 and CD117. Subsequent statistical analysis of immunohistochemical data in relation to diagnosis was performed. Results: The diagnosis of PTC was significantly associated with Strong diffuse Ck19 expression, P63 expression and negative CD56 in relation to studied non PTC follicular thyroid lesions. On the other hand, CD117 was negative in most of the studied thyroid lesions with no significant difference between PTC and other lesions. CK19 was the most sensitive marker (91.2%) and P63 was the most specific one (87.5%), with better specificity in combining markers. Expression of CK19 and lost CD56 provided 97.1% sensitivity and 91.2% diagnostic accuracy in differentiating PTC from other studied lesions. Conclusions: Immunohistochemical markers, Ck19, P63 and CD56 are helpful in diagnosis of PTC and their combination can further improve diagnostic accuracy. CD117 is of no value in the diagnosis of studied cases.