Preoperative BRAFV600E mutation detection in thyroid carcinoma by immunocytochemistry

Abstract

The BRAF^V600E (BRAF) mutation is present in 40-50% of papillary thyroid carcinomas (PTC) and has been associated with more aggressive clinicopathological characteristics of PTC. The aim of this study was to evaluate different methods for preoperative identification of the BRAF mutation in PTC using cytological and histological specimens. Prospectively collected preoperative cytological clots from patients with suspected PTC were tested with BRAF immunocytochemistry (ICC) and the Cobas Test (PCR). In addition, histological specimens were tested with BRAF immunohistochemistry (IHC) and the Cobas Test. All nodules were histologically examined. Fifty-three patients were included in the study. Complete mutation testing was available in 32 patients. The main reason for exclusion was insufficient cell content in the cytological specimen. Twenty-seven nodules were histologically diagnosed as PTC, and 41% (n = 11) of PTCs were BRAF ICC positive. All non-PTC nodules were negative by BRAF ICC. In 26 nodules, all four BRAF tests were concordant, while discordant test results were found in six nodules. ICC was in accordance with the consensus BRAF status in five of these nodules, while BRAF status was undetermined in one nodule. BRAF ICC showed high concordance with the Cobas Test and a low rate of false negative stain. These results indicate that BRAF ICC may be a feasible method for preoperative detection of the BRAF^V600E mutation in patients with PTC.

Keywords: BRAF; Thyroid; diagnosis; immunocytochemistry; thyroid carcinoma.

Fig. 1

Flowchart, patient inclusion. n = number.

Fig. 2

BRAF^V600E stain (red color) of thyroid tumor specimens. (A) BRAF positive cytological clot. (B) BRAF negative cytological clot. (C) BRAF weakly positive cytological clot. (D) Histological sample illustrating a demarcated BRAF positive tumor area (red color, right site) and normal parenchyma with negative BRAF stain (left site).

Fig. 3

Comparison of cytological specimens. (A) Hematoxylin–Eosin (HE) stained cytological clot with papillary thyroid carcinoma micro‐biopsies. (B) Giemsa‐stained conventional smear.