BRAF and RAS mutational status in non-invasive follicular thyroid neoplasm with papillary-like nuclear features and invasive subtype of encapsulated follicular variant of papillary thyroid carcinoma in Korea.

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<i>BRAF</i> and <i>RAS</i> mutational status in non-invasive follicular thyroid neoplasm with papillary-like nuclear features and invasive subtype of encapsulated follicular variant of papillary thyroid carcinoma in Korea.

Thyroid. 2018 Feb 14;:

Authors: Kim M, Jeon M, Oh HS, Park S, Kim TY, Shong Y, Kim WB, Kim K, Kim WG, Song DE

Abstract
BACKGROUND: Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is an indolent thyroid tumor previously known as non-invasive subtype of encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC). The absence of <i>BRAF^V600E</i> mutations has been considered characteristic of NIFTPs. However, a recent study from Korea found that 28.6% of NIFTPs harbored a <i>BRAF</i> mutation. In this study, we evaluated <i>BRAF</i> and <i>RAS</i> mutations in NIFTPs and invasive subtype of EFVPTCs.
METHODS: This study enrolled 32 patients with NIFTP and 48 with invasive EFVPTC. <i>BRAF</i>, <i>NRAS</i>, <i>HRAS</i>, and <i>KRAS</i> mutations were evaluated by direct sequencing using DNA from fresh-frozen tissues and formalin-fixed, paraffin-embedded tissue samples.
RESULTS: The primary tumor size of NIFTP was smaller than that of invasive EFVPTC (median 2.8cm vs. 3.2cm, <i>p</i> = 0.03). Cervical lymph node metastases were found in only four patients with invasive EFVPTC (8%). There was no <i>BRAF</i> mutation in NIFTPs, whereas invasive EFVPTCs had three <i>BRAF^V600E</i> mutations (6%) and one <i>BRAF^K601E</i> mutation (2%). <i>RAS</i> mutations were detected in 15 NIFTPs (47%) and 22 invasive EFVPTCs (46%). <i>NRAS</i> mutations in codon 61 were the most common mutations in NIFTPs (34%) and invasive EFTPTCs (27%). There was no significant difference in the frequency of <i>RAS</i> mutations between the two groups.
CONCLUSIONS: There was no <i>BRAF</i> mutation in any of the NIFTPs. <i>RAS</i> mutations, particularly mutations in codon 61 of <i>NRAS</i>, were the most common mutations in both NIFTPs and invasive EFVPTCs. The presence of a <i>RAS</i> mutation is not helpful for preoperative differentiation between NIFTPs and invasive EFVPTCs.

PMID: 29439609 [PubMed - as supplied by publisher]

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