Are molecular tests necessary to diagnose NIFTP?

Abstract

In 2016, encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) was reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). In 2018 the criteria for NIFTP were widened by the inclusion of the complete lack of papillae. Secondary criteria, which include molecular examination, are helpful but not required for NIFTP diagnose. The aim of this study was to assess the molecular background of NIFTP and to answer the question if the aplication of revised criteria for NIFTP diagnosis is associated with the lack of oncogenic mutation. Repeat histopathological assessment of 1117 cases of papillary thyroid carcinoma (PTC) from 2000-2016 was conducted. Using initial (2016) and revised (2018) diagnostic criteria, NIFTP was diagnosed in 23 and 13 patients respectively. 50 tumor genes hotspots mutation analysis was conducted. BRAF ^V600E mutations were detected in patients who fulfilled only initial NIFTP criteria. Other high-risk mutations (TP53) were found in both groups of patients. The application of restrictive, revised diagnostic criteria for NIFTP negates the need for BRAF ^V600E examination, but these tumors still can harbor other high-risk oncogenic mutations nonetheless. Thus, molecular examination should be considered as a necessary step in NIFTP diagnostic process.