Effect of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP) on Malignancy Rates in Thyroid Nodules: How to Counsel Patients on Extent of Surgery.

ABSTRACT

PURPOSE: To investigate the impact of the nomenclature change to "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) on reported malignancy rates following thyroidectomy. METHODS: Retrospective cohort study of patients with thyroid nodules sampled preoperatively with fine-needle aspiration (FNA) and subsequently removed at one tertiary-care hospital from 4/2016 to 2/2017. Surgical procedure, anatomic pathology, thyroid cytopathology classification, and demographic characteristics were recorded. RESULTS: Thyroidectomy was performed in 353 patients. Twenty-six patients (7.3%) had NIFTP on anatomic pathology. Preoperative FNA demonstrated atypia of undetermined significance (AUS/Bethesda III) in 13 (50%), suspicious for malignancy (SUS/Bethesda V) in 6 (23%), suspicious for follicular neoplasm (SFN/Bethesda IV) in 4 (15%), benign/Bethesda I in 2 (8%), and malignant/Bethesda VI in 1 (4%). Invasive malignancy rates across cytologic categories changed as follows benign (n = 74) from 4 to 1%, AUS (n = 85) from 33 to 18% (p < 0.05), SFN (n = 58) from 29 to 22%, SUS (n = 33) from 91 to 73% (p < 0.05), and malignant (n = 99) from 99 to 98%. Overall decrease in invasive malignancy was 7.3% for the entire population and 13.1% for indeterminate preoperative FNA cytology (Bethesda III-V). Among 26 NIFTP patients, 17 had thyroid lobectomy (TL) and 9 underwent total thyroidectomy (TT). Eight of the nine patients with TT could have been definitively treated with TL, an 89% decrease. CONCLUSIONS: The NIFTP nomenclature change led to an overall decrease in the malignancy rate at our institution, especially for Bethesda III-V categories. Patients may be counseled toward more conservative surgical options if NIFTP is in the differential.