Interobserver and intraobserver variation in the morphological evaluation of noninvasive follicular thyroid neoplasm with papillary-like nuclear features in Asian practice

Abstract

To evaluate the current diagnostic criteria in reportingnuclearfeaturesofnoninvasivefollicularthyroidneoplasmwithpapillary-likenuclearfeatures(NIFTP), nineAsianpathologists with expertise inthyroidreviewed virtual slides of 30noninvasivefollicularpatternedthyroidlesions according to thenuclearscoring system originally proposed by an international expert and a more detailed scoring system proposed by theAsianWorking Group. Theinterobserveragreement fornucleargrading score was generally moderate (kappa value = 0.452). The best consistency fell on the chromatinfeatures(kappa value = 0.658-1.000). A fair to moderateinterobserveragreement was demonstrated in theevaluationofnuclearelongation,nuclearoverlapping, membrane irregularities and distribution of papillarythyroidcarcinoma (PTC) typenuclearfeatures. A slight agreement was rendered for theevaluationof thenuclearenlargement.Intraobserveragreement was substantial to perfect when comparing results of both scoring systems. However, both scoring systems were not able to reliably separate NIFTP from an encapsulatedfollicularvariant PTC with minimal lymph node metastasis or BRAFV600Emutation. Although the three-pointnuclearscoring system for the diagnosis of NIFTP is widely used inAsianpractice,interobservervariationwas considerable. Ancillary immunohistochemical or molecular testing might be helpful in differentiating NIFTP from true PTC.