Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP): Prevalence, Molecular and Ultrasonographic Profiles, and Cyto-Histo Correlation

Document Type

Conference Proceeding

Publication Date

3-1-2024

Publication Title

Lab Invest

Abstract

Background: Non-invasive follicular thyroid neoplasm with papillary like nuclear features (NIFTP) was introduced in 2017 WHO Classification of Endocrine Tumors. The diagnosis of NIFTP requires surgical excision specimen with thorough evaluation of the tumor-host interface. Thyroid Imaging Reporting and Data Systems (TIRADS) score and fine needle aspiration (FNA) results are useful for triaging thyroid nodules; molecular tests such as Afirma may serve as an adjunct method. This study examined the prevalence of NIFTP, summarized and analyzed results of Afirma, imaging, and FNA results in NIFTP cases at our institution. Design: All consecutive thyroid resections at our institution between 2018-2022 were included, including lobectomies, hemithyroidectomies, thyroidectomies, and completion thyroidectomies. Pathological findings were collected from our pathology archives. Clinical information was collected from medical records. Results: In the study period, 1281 thyroid resections were identified. NIFTP was diagnosed in 110 cases (8.6%, average age 53.9, female to male ratio (F/M): 2.5). Of 110 NIFTP cases, 66 were the targeted lesions with an average size of 2.5 cm (60%, average age 51.4, F/M: 2). Of the 66 targeted nodules, 28 were sent for Afirma testing, 45 cases had TIRADS scores in the imaging report, and 54 cases had an FNA performed at our institution. Of the 28 cases with Afirma reports, 24 cases were labeled “suspicious”, including four with RAS-related mutations (risk of malignancy (ROM) 75%) and one with BRAFV600E mutation (ROM 99%) (misclassified as NIFTP on re-review). The majority of the suspicious cases, however, don’t have a specific/reportable genetic alternation (ROM 50%) (Fig. 1). Of the 45 cases with TIRADS score, 60% were classified as TIRADS 4. Of the 54 cases with previous FNA, the majority of cases had a diagnosis of AUS/FLUS or FN (AUS/FLUS: 29 cases (53.7%); FN: 17 cases (31.5%)), while other diagnoses included non-diagnostic (3), benign (5), suspicious (1), and PTC (3) (Table 1). Lastly, 44 NIFTP were identified incidentally during resections for malignancy (18 PTCs, 1 FC, 43.2%), completion thyroidectomies (8, 18.2%), and resections for benign conditions (17, 38.6%). Conclusions: 1) The majority of the targeted NIFTPs had “suspicious” Afirma results, TIRADS 4 scores (60%) and either AUS/FLUS (53.7%) or FN (31.5%) FNA results. 2) Molecular testing may be sent and results need to be reviewed before making the diagnosis of NIFTP.

Volume

104

Issue

3

First Page

S497

Last Page

S498

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