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

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 BethesdaSystem for Reporting Thyroid Cytopathology has not been well reported in Singapore.Methods: We retrospectively identified 821 thyroid nodules with preoperative FNAC from 788 patientsout of 1,279 consecutive thyroidectomies performed between January 2010 and August 2016 in a tertiarygeneral hospital in Singapore. Possible cases of NIFTP were reviewed for reclassification and theimpact of NIFTP on ROM was analysed.Results: The incidence of NIFTP was 1.2% (10 out of 821). If NIFTP is considered benign, ROM inBethesda 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-upof 15 to 110 months. One had possible rib metastasis as evidenced by I131 uptake but remained freeof structural or biochemical disease during a follow-up period of 110 months. None had lymph nodemetastasis at presentation, nor locoregional or distant recurrence.Conclusion: Classifying NIFTP as benign decreased ROM in Bethesda II through VI, but the benignityof NIFTP requires more prospective studies to ascertain. The impact of NIFTP on ROM in our institutionalso appears to be lower than that reported in the Western studiesKeywords: Bethesda, cytology, NIFTP, risk of malignancy, TBSRTC, thyroid nodule