The aim of the study was to assess interobserver variation in reporting nuclear features of encapsulated follicular variant of papillary thyroid carcinoma, newly reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), based on a proposed standardized scoring system. An education module was individually reviewed as a pre-evaluation teaching guide of the specific features of classical papillary carcinoma, the specific inclusion and exclusion features for the diagnosis of NIFTP, and a catalog of the standardized scoring system of the nuclear features of papillary carcinoma used to reach this diagnosis. Participants subsequently reviewed 30 cases of thyroid lesions previously scored by members of the Endocrine Pathology Society Working Group for the Re-evaluation of the Encapsulated Follicular Variant of Papillary Thyroid Carcinoma. There was one uninvolved reference image to demonstrate fixation, processing, and cell size and one image from each case for scoring, with results recorded for each participant. The location of training (country and program), years as a practicing pathologist, and approximate number of thyroid gland surgical cases diagnosed per year were recorded. The degree of agreement between participants was assessed by kappa statistics, using the individual criteria and the average composite scores of the Working Group as a point of comparison. Using the Nuclear Standardized Scoring System, the interobserver agreement for final diagnosis score was generally excellent: unweighted and weighted kappa values between individual observers ranging from 0.242 to 0.930 (average 0.626). There was significant agreement between observers in reaching an interpretation of the presence or absence of nuclear features to diagnose NIFTP (score 0–1 versus score of 2–3), with California pathologists, 0.63 (median 0.66, SD 0.15); Japanese pathologists, 0.64 (median 0.66, SD 0.16); and UK pathologists, 0.60 (median 0.57, SD 014) compared to the expert panel, 0.70 (median 0.73, SD 0.19). The use of the nuclear scoring system to evaluate the nuclear features of papillary thyroid carcinoma as applied to reach the diagnosis of NIFTP shows a good to substantial interobserver agreement, suggesting that consensus can be reached in diagnosing the nuclear features required for this newly reclassified neoplasm.
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With appreciation to all pathologists who participated in this study, including 21 participants from the Southern California Permanente Medical Group and the Naval Medical Center-San Diego, 30 participants from various universities and hospitals in Japan, and 26 participants from the UK and Ireland, 20 of whom are members of the UK Endocrine Pathology Society.
This article does not contain any studies with human participants performed by any of the authors and thus informed consent was not required.
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The authors declare that they have no conflict of interest.
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Thompson, L.D.R., Poller, D.N., Kakudo, K. et al. An International Interobserver Variability Reporting of the Nuclear Scoring Criteria to Diagnose Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: a Validation Study. Endocr Pathol 29, 242–249 (2018). https://doi.org/10.1007/s12022-018-9520-0
- Thyroid neoplasms
- Thyroid cancer, papillary
- Carcinoma, papillary follicular/pathology
- Observer variation
- Scoring system