Variation in the Diagnosis of Noninvasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features

Abstract

Context Noninvasive encapsulated follicular variant of papillary thyroid cancer (EFVPTC) was reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in January 2017. The impact of this nomenclature change at a population level remains unknown. Objective Examine use of NIFTP across different US regions and populations. Design Descriptive epidemiology study using SEER-22 data (2000-2019). Participants Individuals diagnosed with papillary or follicular thyroid cancer (2000-2019), or NIFTP (2017-2019). Main outcome measures Annual incidence rates of thyroid cancer by subtype and NIFTP. Using 2018-2019 data: 1) rates of NIFTP at the 17 SEER-22 sites, and 2) comparison of demographics for patients diagnosed with NIFTP versus papillary and follicular thyroid cancer. Results NIFTP comprised 2.2% and 2.6% of cases in 2018 and 2019, respectively. Between 2018-2019, large heterogeneity was observed in the regional use of NIFTP diagnosis, with site-specific incidence rates between 0.0-6.2% (median 2.8%, IQR 1.3-3.6%). A diagnosis of NIFTP (vs papillary and follicular thyroid cancer) was significantly associated with older age (P=0.012 and P=0.009), Black race (both P<0.001), and non-Hispanic ethnicity (both P<0.001) for 2018 and 2019, respectively. Conclusions Marked variation exists in the use of the NIFTP diagnosis. The recent 2021 coding change that resulted in NIFTP, a tumor with uncertain malignant potential and for which there is no long-term outcome data available, no longer being a reportable diagnosis to SEER will disproportionately affect vulnerable patient groups such as older patients and Black patients, in addition to patients who reside in regions with higher rates of NIFTP diagnoses.

Probability of malignancy and molecular alterations as determined by ThyroSeq v3 genomic classifier in Bethesda Category IV

“…This may be attributed to our institutional practices, as demonstrated in our previous study by Gajzer et al ., in which we reported a higher prevalence of NIFTPs in aspirates with cytologic atypia in BIII 6 . Based on surgical resections diagnosed between 2018 and 2022, our institution's rate of NIFTP is approximately 3% (65 of 1991 lobectomy/thyroidectomy cases), comparable with findings from other studies 25, 26 . This observation emphasizes the critical role of considering institutional practices and previous studies when interpreting and comparing results.…”

“…6 Based on surgical resections diagnosed between 2018 and 2022, our institution's rate of NIFTP is approximately 3% (65 of 1991 lobectomy/thyroidectomy cases), comparable with findings from other studies. 25,26 This observation emphasizes the critical role of considering institutional practices and previous studies when interpreting and comparing results. By acknowledging the influence of institutional practices, we can better evaluate the significance and generalizability of our findings.…”

Papillae, psammoma bodies, and/or many nuclear pseudoinclusions are helpful criteria but should not be required for a definitive cytologic diagnosis of papillary thyroid carcinoma: An institutional experience of 207 cases with surgical follow up

“…2.2% to 2.6% of thyroid cancers in 2018-2019 vs. 18.6% of PTC estimated by EPS. 50 These data suggest that the impact of NIFTP is not as considerable as initially estimated, and variations in incidence may be a result of variation of cancer rates in different populations, and/or variations in the interpretation of PTC nuclear atypia, which is still subjective despite efforts to objectify it. 51 Therefore, each center should consider basing their clinical decisions on their own data, including incidence of NIFTP in their patient population, and their thresholds for diagnosing PTC.…”

“…A comprehensive metanalysis found that worldwide incidence of NIFTP (6% of PTC) is much lower than initially estimated, and significantly lower in Asian countries (2.1%) compared with Western countries (9.3%–9.6%) 49 . A recently published epidemiology study using SEER‐22 data, by Chen et al., reported that NIFTP comprised a small fraction of previously diagnosed thyroid cancers, which was significantly less than was anticipated by EPS: 2.2% to 2.6% of thyroid cancers in 2018–2019 vs. 18.6% of PTC estimated by EPS 50 . These data suggest that the impact of NIFTP is not as considerable as initially estimated, and variations in incidence may be a result of variation of cancer rates in different populations, and/or variations in the interpretation of PTC nuclear atypia, which is still subjective despite efforts to objectify it 51 .…”