The correlation of sodium iodide symporter and BRAFV600E mutation in classical variant papillary thyroid carcinoma ★★★

• Functional sodium iodide symporter (NIS) expression is higher in patients with classical variant papillary thyroid carcinoma with BRAFV600E mutation.
• The clinical features were not found to be associated with NIS expression.
• There may be different mechanisms determining the outcome of therapy.

BRAFV600E mutation was analyzed by real-time polymerase chain reaction in 96 consecutive cases with classical variant papillary thyroid cancer, and immunohistochemical staining of Na +/I − symporter (NIS) protein was evaluated. Localization (intracellular or membranous), density, and the intensity of cytoplasmic staining were characterized semiquantitatively. Extrathyroidal invasion, surgical margin positivity, and lymph node metastasis were compared with BRAFV600E mutation and NIS expression. Eighty-eight patients who had at least 24-month follow-up were also included in survival analysis. BRAFV600E mutation was determined in 78.1% (75/96) and functional NIS activity in 74% (71/96) of the cases. There were statistically significant differences in mean ages between BRAFV600E mutation–positive (48.6) and BRAFV600E mutation–negative cases (37.3; Levene test, P = .419; Student t test, P = .001). The surgical margin positivity (46.7%) and extrathyroidal extension percentage (54.7%) in the BRAFV600E mutation–positive group were higher than the negative (28.6% and 33.3%, respectively) group, without statistical significance (P = .138 and P = .084, respectively). Functional NIS activity was higher in BRAFV600E mutation–positive cases (78.1%) than mutation-negative ones (57.1%; P = .047). The possibility of moderate and intense cytoplasmic staining in BRAFV600E mutation–positive cases (72%) was 6.3 times higher than the possibility of weak staining (28%) in the mutation-positive cases (95% confidence interval, 2.2-18.8; P = .001). Functional NIS expression is higher in patients with classical variant papillary thyroid cancer with BRAFV600E mutation. However, the clinical features were not found to be associated with NIS expression. There may be different mechanisms determining the outcome of therapy.