Prediction of classical versus non classical papillary thyroid carcinoma subtypes from cytology of nodules classified according to TIRADS

PURPOSE

Our purposes were: 1) to estimate the prediction performance (PP) of cytology in identifying papillary thyroid carcinoma (PTC) subtypes; 2) to explore how the PTC subtypes distribute among the American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS) categories.

METHODS

Nodules were included if both the histology with the PTC subtype report and the cytology report with the possible PTC subtype were available. The PP was calculated by making the proportion of True positives/False positives+false negatives.

RESULTS

309 cytologically "suspicious for malignancy" and "malignant" thyroid nodules with PTC histology were evaluated. ACR TI-RADS categorization for classical PTC was significantly different from non-classical PTC (p-value 0.02). For the whole cohort the PP of cytologically classical cases was 0.74, while that of cytologically non classical cases was 0.41. ACR TI-RADS categorization was not significantly different for aggressive vs non-aggressive PTC subtypes (p-value 0.1). When considering only aggressive or non-aggressive PTC subtypes, the PP of cytologically classical cases was respectively 0.86 and 0.87, while that of cytologically non classical cases was respectively 0.27 and 0.22. The PP of cytologically classical cases was 0.73 and 0.79, respectively for macroPTCs and microPTCs, while that of cytologically non classical cases was 0.55 and 0.33, respectively for macroPTCs and microPTCs.

CONCLUSION

Cytology examination reliably performed in predicting classical PTC versus non classical PTC subtypes. ACR TI-RADS categorization was significantly different among classical PTC versus non classical PTC subtypes.

Analysis of a pre-2017 follicular variant papillary thyroid carcinoma cohort reclassified as noninvasive follicular thyroid neoplasm with papillary-like features (NIFTP): an 11-year retrospective single institution experience

INTRODUCTION

Noninvasive follicular thyroid neoplasm with papillary-like features (NIFTP), represents a distinct class of thyroid neoplasms with very low risk of adverse outcome and a set of strict histologic criteria. Introduction of NIFTP as a non-cancer has had an appreciable decrease in risk of malignancy and body of literature on this entity continues to grow. In this study, we reviewed clinical, fine-needle aspiration cytology (FNAC), imaging, and molecular findings of histologically proven NIFTPs at our institution.

MATERIALS AND METHODS

Thyroid resections during an 11-year period, with histologic diagnosis of follicular variant of papillary thyroid carcinoma (FVPTC), were retrospectively reviewed to identify NIFTP. Ultrasonographic appearance, FNA findings, and molecular findings were also reviewed.

RESULTS

Of 244 cases of FVPTC identified, 74 (30%) cases were reclassified as NIFTP. Mean tumor size was 2.5 cm. Of 33 patients with lymph node dissection, none had lymph node metastases. On imaging, 36 NIFTP (49%) showed vascularity, 25 (33%) were isoechoic to hypoechoic, there were calcifications in 14 cases (19%), and 7 cases (9%) showed a hypoechoic rim. Bethesda III/IV was the most common interpretation rendered on FNAC (31%). Seven cases had NRAS mutations and 1 case had BRAF V600E mutation. The remaining cases were either negative for BRAF V600E or had no identifiable molecular alterations.

CONCLUSIONS

A significant percentage of tumors previously diagnosed as FVPTC were reclassified as NIFTP. This tumor cannot be reliably diagnosed preoperatively on FNAC, shows no characteristic features on ultrasound and has low suspicion of malignancy. BRAF V600E mutations are infrequent in NIFTP.

The Incidence of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: A Meta-Analysis Assessing Worldwide Impact of the Reclassification

Background: Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) reclassification has significantly influenced the field of thyroidology. However, the extent of this impact depends upon the incidence of NIFTP in a given population. In this meta-analysis, we aimed to obtain robust information about the actual incidence of NIFTP worldwide by reviewing the published data. Methods: Comprehensive literature search was performed using electronic databases of PubMed and Web of Science over a five-year period (January 1, 2016, to January 30, 2021). The incidence of NIFTP was calculated by dividing the number of NIFTPs by the number of papillary thyroid carcinomas (PTCs). Meta-analysis of proportion and their 95% confidence interval [CI] were pooled using the random-effect model. Heterogeneity across the included studies was assessed using I² statistics. Egger's regression test and funnel plot of estimates were used to evaluate the publication bias. p-Value <0.05 was considered significant. Results: From 505 publications, we included 50 studies, all retrospective, with 100,780 PTCs and 3990 NIFTP from 92 institutions worldwide. The overall incidence of NIFTP was 6.0% [CI 4.4-8.2] among PTCs or thyroid malignancies with a high level of heterogeneity among the included studies (I² = 98.6%). NIFTP incidence was largely similar in North America and Europe (9.3% vs. 9.6%), with a significantly lower overall rate in Asia (2.1%). There was a significant decline in the reported incidence of NIFTP in non-Asian studies published after 2017 (p = 0.002). On applying our data on global thyroid cancer statistics, this reclassification would affect ∼30,881 patients annually, with a lower impact in Asia compared with North America and Europe. Conclusions: This comprehensive meta-analysis confirms that the worldwide NIFTP incidence is much lower than estimated initially. The NIFTP rates are significantly lower in Asian compared with North American and European countries. Apart from geography, NIFTP rates are significantly influenced by the nature of study, type of database used for sample collection, and the diagnostic criteria used. Introduction of NIFTP may potentially spare over 30,000 patients worldwide annually from clinical and psychological consequences of a thyroid cancer diagnosis.

Influence of Nomenclature Changes on Trends in Papillary Thyroid Cancer Incidence in the United States, 2000 to 2017

CONTEXT

US papillary thyroid carcinoma (PTC) incidence recently declined for the first time in decades, for reasons that remain unclear.

OBJECTIVE

This work aims to evaluate PTC incidence trends, including by histologic subtype and size, and noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP).

DESIGN

This descriptive study uses US Surveillance, Epidemiology, and End Results-18 cancer registry data (2000-2017).

PATIENTS

Participants included individuals diagnosed with PTC (2000-2017) or NIFTP (2016-2017).

RESULTS

During 2000 to 2015, PTC incidence increased an average 7.3% per year, (95% CI, 6.9% to 7.8%) during 2000 to 2009, and 3.7% per year (95% CI, 0.2% to 7.3%) during 2009 to 2012, before stabilizing in 2012 to 2015 (annual percentage change [APC] = 1.4% per year, 95% CI, -1.8% to 4.7%) and declining in 2015 to 2017 (APC = -4.6% per year, 95% CI, -7.6% to -1.4%). The recent declines were observed for all sizes of PTC at diagnosis. Incidence of follicular variant of PTC (FVPTC) sharply declined in 2015 to 2017, overall (APC = -21.1% per year; 95% CI, -26.5% to -15.2%) and for all tumor sizes. Observed increases in encapsulated papillary carcinoma (classical PTC subtype) and NIFTP each accounted for 10% of the decline in FVPTC. Classical PTC incidence continuously increased (2000-2009, APC = 8.7% per year, 95% CI, 8.1% to 9.4%; 2009-2017, APC = 1.0% per year, 95% CI, 0.4% to 1.5%), overall and for all sizes except smaller than 1 cm, as did incidence of other PTC variants combined (2000-2017, APC = 5.9% per year, 95% CI, 4.0% to 7.9%).

CONCLUSION

The reasons underlying PTC incidence trends were multifactorial. Sharp declines in FVPTC incidence during 2015 to 2017 coincided with clinical practice and diagnostic coding changes, including reclassification of noninvasive encapsulated FVPTC from a malignant to in situ neoplasm (NIFTP). Observed increases in NIFTP accounted for 10% of the decline in FVPTC.

Ultrasound findings of noninvasive follicular thyroid neoplasm with papillary-like nuclear features compared with those of follicular variant of papillary carcinoma and encapsulated papillary carcinoma: a single-institution study in Japan

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a new entity adopted by the newest World Health Organization classification. It is differentiated from follicular variant papillary thyroid carcinoma (FVPTC) and regarded as non-malignant disease. Here, we compared the ultrasound findings of NIFTP (n = 40) with those of FVPTC (n = 94) and encapsulated PTC (encap-PTC) (n = 157). The NIFTP group showed benign findings on ultrasound significantly more frequently than the FVPTC group based on the Japan Society of Ultrasonics in Medicine criteria: a regular shape (p < 0.001), well edge definition (p = 0.007), smooth character (p < 0.001), isoechoic and homogeneous internal echoes (p < 0.001), lack of punctate microcalcification (p = 0.027), and a regular marginal hypoechoic zone (p < 0.001). Compared to encap-PTC, NIFTP has a significantly higher incidence of benign findings: isoechoic and homogeneous internal echoes (p < 0.001), lack of punctate microcalcification (p < 0.001), and a regular marginal hypoechoic zone (p = 0.004). Based on the ultrasound classification (USC) system at Kuma Hospital, no cases were classified as malignant (USC ≥3.5), but 55.4% of the FVPTCs and 53.5% of the encap-PTCs were diagnosed as malignancy. However, on cytology, the incidence of NIFTP classified as Bethesda-V or -VI (PTC) was very high at 86.9%. All patients underwent surgical treatment, but none of the NIFTP patients showed postoperative recurrence. Although avoiding surgery might be difficult because of the high incidence of malignant cytology, overtreatment (including extensive surgery) for NIFTP can be avoided by paying close attention to the lack of malignant findings on ultrasound.

A closer look at NIFTP

Despite the rise in the incidence of papillary thyroid carcinoma (PTC) during the last 30 years, the mortality rate due to PTC has remained static. One reason for this phenomenon is the indolent nature of some of the tumors that are diagnosed as PTC. A subgroup of tumors, which often exhibited such indolent behavior, was encapsulated/well-circumscribed follicular lesions that showed PTC nuclear features. Despite their indolent behavior, these tumors were managed as was any other PTC, often with total thyroidectomy and radioactive iodine (RAI) treatment. In order to prevent overtreatment of these tumors, they were recently reclassified as "non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)." Since it is proposed that NIFTP be managed in a more conservative manner, its diagnosis is now based on strict histological criteria. The genetic basis of these diagnostic criteria and the utility of molecular markers in the diagnosis of NIFTP are currently being scrutinized. The aim of this review is to discuss the events that led to the emergence of the term NIFTP, as well as its histological and molecular background.

Practice Paradigms Before and After Introduction of the Diagnosis-Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP): an Institutional Experience

The recently adopted terminology of "Noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) reflects the indolent behavior of these tumors. In contrast to conventional papillary thyroid carcinomas, NIFTP can be managed conservatively. The purpose of this study was to investigate changes in surgical and pathologic practice patterns at our institution since the introduction of the NIFTP diagnosis in 2016. A retrospective analysis of all thyroid specimens received in our laboratory between January 2015 and April 2017 was performed. The final cohort consisted of 1508 thyroidectomy specimens from 1508 patients (1153 (76.5%) women and 355 (23.5%) men), of which 1011 (67%) were total thyroidectomies and 497 (33%) were partial thyroidectomies. There were 558 (69.2%) total thyroidectomies and 248 (30.8%) partial thyroidectomies performed prior to introduction of the NIFTP diagnosis and 453 (64.5%) and 249 (35.5%) total and partial thyroidectomies, respectively, after the change in nomenclature. Within a year following the initial use of this diagnosis, 67 NIFTP cases were identified (9.5% of all thyroidectomies), whereas compared with the year preceding it, malignant diagnoses decreased from 54.5 (439) to 44.6% (313), and the benign category remained unchanged from 44.5 (367) to 45.9% (322). For the entirely submitted 67 NIFTP cases, the mean number of blocks submitted was 14.7 (0.98 blocks/g); for malignant lesions 17.7 (0.92 blocks/g); and for benign lesions 16.6 (0.75 blocks/g). The results of our study suggest that NIFTP are encountered in almost 10% of thyroidectomies at our institution with expected shifts in cytology and surgical pathology diagnoses as a result of the change in nomenclature. During this time period, significant shifts towards less aggressive surgical management were not observed. All 67 NIFTP nodules were submitted entirely with no significant difference in the number of cassettes submitted for NIFTP nodules as compared with follicular variant papillary thyroid carcinoma (PTC), classic variant PTC, or follicular adenoma.

Did Introducing a New Category of Thyroid Tumors (Non-invasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features) Decrease the Risk of Malignancy for the Diagnostic Categories in the Bethesda System for Reporting Thyroid Cytopathology?

In 2016, Nikiforov et al. (JAMA Oncol 2:1023-1029, 2016) proposed replacing the term "non-invasive encapsulated follicular variant of papillary thyroid carcinoma" (FVPTC) with the term "non-invasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP). In 2018, to avoid the misdiagnosis of papillary thyroid cancer as NIFTP, the authors proposed changes to the criteria for NIFTP classification. Some previous studies evaluated the impact of NIFTP on the risk of malignancy (ROM) in the fine-needle aspiration cytology (FNAC) diagnostic categories according to the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC). However, little is known about the influence of an NIFTP diagnosis on ROM on the basis of the revised criteria. The aim of this study was to assess the influence of NIFTP on ROM using the revised diagnostic criteria. The present study included 998 thyroid nodules that were diagnosed and resected at the same medical center. All specimens with a diagnosis of cancer were reviewed to identify NIFTP according to the revised 2018 criteria. Additionally, molecular diagnostics were performed to detect the BRAF p.V600E mutation and TERT promoter mutations in all the NIFTP cases. The number of cases that met the revised criteria was determined, and the ROM was calculated in each of the FNAC diagnostic categories. Only five cases (2.3% of all papillary thyroid carcinoma diagnoses) were considered NIFTP, according to the 2018 criteria. With respect to the FNAC category, one case was a follicular neoplasm or suspicious for a follicular neoplasm (FN/SFN), three cases were suspicious for malignancy (SM), and one case was malignant (M). The ROM decreased in each of the Bethesda categories (0.7% in FN/SFN, 4.3% in SM, and 0.5% in M) when a diagnosis of NIFTP was taken into account. These reductions were not statistically significant. These data indicate that the NIFTP entity has very little impact on ROM for the diagnostic categories of the Bethesda system.

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP): An Update

Based on evidence accumulated over the past three decades showing that noninvasive encapsulated follicular variant of papillary thyroid carcinoma has an indolent clinical behavior and a RAS-like molecular profile similar to follicular adenoma, the Endocrine Pathology Society working group in 2016 proposed to rename this entity as "noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)" in order to eliminate the term "carcinoma" from the diagnosis. It is a major evidence-based attempt initiated by an international group of endocrine pathologists to tackle the epidemic of thyroid cancer overdiagnosis and overtreatment. However, its creation and continuous existence are not without controversies. NIFTP has sparked a wave of follow up studies aiming to decipher the exact nature of this new entity. In this review, we summarize the rationale, diagnostic criteria, controversies and subsequent changes to the NIFTP concept, and their impact on patient care and pathology practice.

miR-222 expression is correlated with the ATA risk stratifications in papillary thyroid carcinomas

BACKGROUND

miR-222 is one of the most consistently overexpressed miRNAs in papillary thyroid carcinoma (PTC). Previous studies demonstrated that miR-222 overexpression conferred high-risk features in PTC patients, suggesting its value in risk-stratification. However, studies in term of miR-222's utility on stratifying PTCs are lacking.

METHODS

One hundred patients including 10 with multinodular goiter and 90 with PTC were enrolled. Formalin-fixed paraffin-embedded samples were exploited for miR-222 quantitative reverse transcriptase- polymerase chain reaction (RT-PCR) analysis. Correlations between miR-222 expression and different clinicopathological features, Tumor-node-metastasis (TNM) staging and ATA risk level were analyzed.

RESULTS

miR-222 expression of the PTC group was significantly higher than that of the goiter group (P < .001). Furthermore, miR-222 expression was significantly higher in PTCs with advanced features like larger tumor, capsular invasion, vascular invasion and lymph nodes metastasis. The majority of patients (61%) were in stage I group (similar to ATA low-risk) by TNM staging system. As to the ATA system, the majority (73%) were in intermediate-risk group (similar to TNM stage II and III roughly). Contrary to previous report, here we found that miR-222 expression was correlated with the ATA risk level (P < .001), but not with the TNM staging (P = .122).

CONCLUSION

In the present study, we demonstrated that miR-222 overexpression was correlated with advanced features like capsular invasion, vascular invasion, larger tumor size and lymph node metastasis in PTCs. Most importantly, miR-222 expression was correlated with ATA risk levels, suggesting its potential value in PTC risk-stratification.

Ultrasound-guided fine needle aspiration of thyroid nodules with on-site cytological examination: Diagnostic efficacy, prevalence, and factors predicting for Bethesda category I results

BACKGROUND AND OBJECTIVE

Ultrasound-guided fine needle aspiration of thyroid nodules with on-site cytological examination may decrease the number of Bethesda categoryI cytologies. The study objective was to evaluate our second-year experience with this procedure to analyze diagnostic efficacy, prevalence, and factors predicting for Bethesda categoryI results.

PATIENTS AND METHOD

A retrospective study was conducted of 279 nodules from 233 patients. Ultrasound -guided fine needle aspiration was performed according to the 2015 criteria of the American Thyroid Association. A specimen of each aspiration was air-fixed on site before Diff-Quik staining and microscopic examination to assess its suitability; otherwise, nodule aspiration was repeated up to 5times. Diagnostic efficacy was assessed based on sensitivity and specificity on the cytological categories BethesdaII and BethesdaVI.

RESULTS

Diagnostic sensitivity and specificity were both 100%, 5.4% Bethesda categoryI results were obtained, and variables independently associated were age (4.7% increase per year of life) and nodule volume (2.3% increase per each 1mL of volume).

CONCLUSIONS

Ultrasound-guided fine needle aspiration of thyroid nodules with on-site cytological examination allows for a high diagnostic efficacy and has been shown to be a highly relevant procedure because it has a very low rate of cytological results of Bethesda categoryI, whose risk has been higher in older subjects and with larger nodules.

Distinguishing non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) from classic and invasive follicular-variant papillary thyroid carcinomas based on cytologic features

INTRODUCTION

An international panel recently recommended reclassification of non-invasive follicular variant of papillary thyroid carcinoma (PTC) to non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). NIFTPs have little or no risk of recurrence and can be treated with lobectomy alone. Preoperative distinction of NIFTP from PTC will help avoid overtreatment.

MATERIALS AND METHODS

All thyroid tumors with a histologic diagnosis of PTC and preceding diagnostic cytology (n = 299) over a 5-year period were identified. Cases meeting criteria for NIFTP were reclassified as such. All NIFTP cases with available cytology (n = 6) and a similar number of randomly selected invasive follicular variant of papillary thyroid carcinoma (IFVPTC; n = 9) and classic PTC (cPTC, n = 11) were evaluated for 18 cytologic features.

RESULTS

A total of 35 (12%) lesions were reclassified as NIFTP, 194 (65%) were cPTC, and 70 (23%) were IFVPTC. The NIFTPs had a preceding cytologic interpretation of benign (31%), atypia of undetermined significance (34%), follicular neoplasm (9%), suspicious for malignancy (12%), or malignant (14%). Cytologically, NIFTP was distinguished from cPTC by absence of any architectural features in all 6 cases, and by absence of pseudoinclusions (P < 0.001) and multinucleated giant cells (P = 0.027) in nearly all. Nuclear pseudoinclusions (P = 0.001), marginal micronucleoli (P = 0.018), irregular branching sheets (P = 0.025), and linear arrangement (P = 0.025) favored IFVPTC over NIFTP.

CONCLUSIONS

NIFTPs were originally assigned to a variety of cytologic categories. There are several cytologic differences between NIFTP and cPTC or IFVPTC. Our findings support restricting the definitive diagnosis of PTC to cases with architectural features of PTC and/or intranuclear pseudoinclusions.

Reclassification as NIFTP: a Retrospective Review in a Single Institution with an Emphasis on Workload

The aim of this study was to determine the number of cases of papillary thyroid carcinoma (PTC) which could be reclassified as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in our institute over a 10-year period, document their clinical status and assess the number of slides that had to be reviewed per case to exclude NIFTP. The histopathology reports for thyroid resections for all papillary carcinoma over a 10-year period (2007-2016) were reviewed. Five hundred forty-five histopathology reports were reviewed, and 71 cases were identified as potential cases of NIFTP. Forty-nine (69%) cases had been referred from external departments and the slides were not available for review. Of the remaining 22 (31% of 71) cases, 5 were reclassified as NIFTP. The 17 cases that were not reclassified as NIFTP required review of 114 of 356 slides (median 5.5 slides per case) was required to exclude NIFTP. For the 5 NIFTP cases, 58 slides were reviewed (median 12 slides per case). We found that review of the histology reports alone was adequate for exclusion in most cases, e.g. classic PTC or EVPTC cases with documented lymphovascular invasion or capsular invasion. As a single exclusion criterion is required for exclusion from reclassification as NIFTP, this can be achieved efficiently. Two of the five patients received radioactive iodine [RAI] as per standard treatment at time of diagnosis, on the basis of tumour size. None have recurrent or metastatic disease with mean follow-up of 5.8 years.

Small papillary thyroid carcinoma with minimal extrathyroidal extension should be managed as ATA low-risk tumor

PURPOSE

According to American Thyroid Association (ATA) guideline, papillary thyroid cancer (PTC) with minimal extrathyroidal extension (mETE) is classified at "intermediate risk" of persistent/recurrent disease. However, the impact of mETE per se on patients' outcome is not fully understood. The aim of our study was to evaluate the prognostic significance of mETE in patients with PTC not submitted to therapeutic or prophylactic lymph node dissection, according to tumor size and other prognostic factors.

PATIENTS AND METHODS

We retrospectively evaluated a total of 514 PTC patients: 127 (24.7%) had mETE (pT3Nx) and 387 (75.3%) had negative margins (pT1-2Nx). At a median follow-up of 9.1 years, patients were divided in two groups: patients with "good outcome" (no evidence of disease) and patients with "poor outcome" (persistent structural disease or recurrent disease or tumor-related death).

RESULTS

The rate of patients with "poor outcome" was significantly higher in patients with mETE compared with patients with negative margins (11.8 versus 5.1%; OR 2.4576, 95% CI 1.2178-4.9594, p = 0.01). However, mETE was significantly associated with poor outcome only in patients with tumors larger than 1.5 cm.

CONCLUSIONS

mETE is an unfavorable prognostic factor in tumors larger than 1.5 cm, suggesting that, in the absence of other unfavorable characteristics, smaller tumors with mETE should be classified and managed as "low risk" tumors.