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.