Availability of Immunohistochemistry in the Diagnosis of Follicular Variant of Papillary Thyroid Carcinoma

ABSTRACT

BACKGROUND: Making the diagnosis of the follicular variant of papillary thyroid carcinoma (FVPTC) is often difficult, and there are no accurate immunohistochemical or molecular markers. The purpose of this study is to evaluate performing immunohistochemistry to make the diagnosis of FVPTC. METHODS: A total of 249 thyroid lesions were studied. We made the tissue microarray, and we assessed the expression of HBME-1, galectin-3, CD56, and p63. RESULTS: Galectin-3, HBME-1, and p63 were positive in 79.7%, 79.7%, and 15.9% of the FVPTC, respectively. These immunohistochemical features of FVPTC were between those of classic papillary thyroid carcinoma (CPTC) and those of non-PTC. The CD56 expression was positive in 75.4% of the FVPTC, which is much higher than that of the CPTC (28.3%), and even higher than that of the non-PTC lesions (60%). Comparing FVPTC with CPTC, the expression of galectin-3 was significantly higher and the expression of CD56 was significantly lower in the CPTCs. Comparing the FVPTC with follicular carcinoma (FC), the expression of all the markers was significantly higher in the FVPTC. Comparing PTC with FC, the expression of CD56 was lower and the expressions of the other markers were higher in the PTCs. CONCLUSIONS: Galectin-3, HBME-1, and p63 can help make the diagnosis of FVPTC, and a cocktail of these markers can be even more useful. But CD56 is not thought to be useful to make the diagnosis of FVPTC.