Non-invasive follicular thyroid neoplasm with papillary-like nuclear features; a single centre study

Abstract

Introduction: Papillary carcinoma of the thyroid is the commonest cancer in the thyroid with an increasing incidence over the past few decades. A subset of papillary carcinomas was re-classified into "Non-invasive Follicular Thyroid Neoplasm with papillary-like nuclear features" (NIFTP) in late 2017, due to the excellent prognosis they exhibit. Identification of NIFTP is important because surgical management and follow up is similar to follicular adenoma, thus reducing the psychological burden to patient, eliminating unnecessary exposure to radiation and economic burden to the society. This study intended to assess the prevalence and the inter-observer consistency in identifying NIFTP in the study sample.Methods: This retrospective, descriptive, cross-sectional study included all thyroid specimens received at our department in 2017. Thyroid neoplasms with a potential for reclassification to NIFTP were reassessed according the WHO criteria by two investigators who were blinded to the previous and each other's diagnoses.Results: Out of the 256 thyroid specimens received, 74/256 (28.90%) considered to have potential to be reclassified as NIFTP which included 34 cancers. Only 5/74 (6.75%) satisfied the criteria for NIFTP. Three NIFTPs had been reported as papillary microcarcinoma and the other two as follicular variant of papillary carcinoma. Inter-observer consistency in re-classifying the 74 tumours was 94.6%, with a 100% consistency in diagnosing NIFTP. Following re-classification, the proportion of cancers in the study sample reduced to 56/256 (21.87%) from 61/256 (23.82%). The prevalence of NIFTP in the study sample was 1.95% (5/256). Conclusions:The prevalence of NIFTP in the study sample is comparable to the Asian population. The current study reports a high inter-observer consistency in recognizing NIFTP among potential lesions, most likely due to the strict adherence to WHO criteria.