Noninvasive follicular thyroid neoplasm with papillary-like nuclear features and the risk of malignancy in thyroid cytology: Data from Singapore

Abstract

Introduction: The impact of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) on the risk of malignancy (ROM) in fine-needle aspiration cytology (FNAC) per The Bethesda System for Reporting Thyroid Cytopathology has not been well reported in Singapore. Methods: We retrospectively identified 821 thyroid nodules with preoperative FNAC from 788 patients out of 1,279 consecutive thyroidectomies performed between January 2010 and August 2016 in a tertiary general hospital in Singapore. Possible cases of NIFTP were reviewed for reclassification and the impact of NIFTP on ROM was analysed. Results: The incidence of NIFTP was 1.2% (10 out of 821). If NIFTP is considered benign, ROM in Bethesda I through VI were 8.6%, 3.5%, 26.3%, 20.0%, 87.7%, 97.0% versus 8.6%, 4.2%, 28.1%, 26.7%, 89.2% and 100% if NIFTP is considered malignant. Eight patients with NIFTP had follow-up of 15 to 110 months. One had possible rib metastasis as evidenced by I131 uptake but remained free of structural or biochemical disease during a follow-up period of 110 months. None had lymph node metastasis at presentation, nor locoregional or distant recurrence. Conclusion: Classifying NIFTP as benign decreased ROM in Bethesda II through VI, but the benignity of NIFTP requires more prospective studies to ascertain. The impact of NIFTP on ROM in our institution also appears to be lower than that reported in the Western studies Keywords: Bethesda, cytology, NIFTP, risk of malignancy, TBSRTC, thyroid nodule

Prevalence and diagnostic significance of non‐invasive follicular thyroid neoplasm with papillary‐like nuclear features in Japan—A multi‐institutional study

“…However, the reason for the low frequency of NIFTP in Asia remains unclear. Some speculations, such as variation in the prevalence of follicular variants among PTCs, racial and ethnic predispositions to PTC, indications for surgery, and varying thresholds for diagnosing nuclear features of PTC, have been proposed 11–15 . In Western countries, molecular testing using aspirated materials is common, and NIFTP with an RAS mutation is considered a surgical target, with total thyroidectomy remaining an acceptable option for some cases ultimately defined as NIFTP 16,17 .…”

“…Some speculations, such as variation in the prevalence of follicular variants among PTCs, racial and ethnic predispositions to PTC, indications for surgery, and varying thresholds for diagnosing nuclear features of PTC, have been proposed. [11][12][13][14][15] In Western countries, molecular testing using aspirated materials is common, and NIFTP with an RAS mutation is considered a surgical target, with total thyroidectomy remaining an acceptable option for some cases ultimately defined as NIFTP. 16,17 In contrast, in Asian countries where molecular testing is less readily available, 18 active surveillance is commonly adopted for patients with indeterminate thyroid nodules.…”

Performance of a multigene genomic classifier and clinical parameters in predicting malignancy in a Southeast Asian cohort of patients with cytologically indeterminate thyroid nodules

“…27 In our practice, the impact of NIFTP on the malignancy rate of Bethesda categories appears to be lower, although we observed a higher frequency and malignancy rate in the Bethesda III category. 28 American Joint Committee on Cancer eighth edition tumor, lymph node, metastasis (TNM) thyroid cancer staging was used, and the risk of cancer recurrence was based on ATA guidelines. 25…”