Case Report: Multifocal non-invasive follicular thyroid neoplasm with papillary-like nuclear features presenting in a female child

Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was introduced as a separate entity by the World Health Organization in 2017 with strict inclusion and exclusion criteria.  Most NIFTP cases have been reported in adults and few cases have been diagnosed in children. Here, we present a classic case of NIFTP affecting a 10-year old female child. We also review previous reports of NIFTP in children regarding size, focality, nodal metastasis, recurrence, type of operation and follow-up data. The present report adds a new case of NIFTP in the paediatric age group characterized by multifocality, absence of nodal invasion and indolent course until last follow-up, recommending less aggressive management.

Impact of Noninvasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features on Revised Bethesda System Malignancy Rates at a Single Institution

BACKGROUND

The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) standardizes thyroid cytopathology reporting in six tier diagnostic categories. In recent years, noninvasive encapsulated follicular variant of papillary thyroid carcinoma was reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). This study examines the impact of NIFTP on the BSRTC risk of malignancy (ROM).

METHODS

This was a retrospective review of prospectively collected data from 565 patients who underwent fine needle aspiration and thyroidectomy at a single institution. ROM for each Bethesda category was analyzed and calculated with NIFTP classified as a malignant and nonmalignant lesion. Absolute and relative differences between ROM were compared.

RESULTS

Of 565 patients, 19 were Bethesda I, 159 were Bethesda II, 178 were Bethesda III, 46 were Bethesda IV, 42 were Bethesda V, and 121 were Bethesda VI. ROM differences with NIFTP classified as malignant versus nonmalignant for each class were as follows: Bethesda I, no change; Bethesda II, 18%-14%; Bethesda III, 55%-48%; Bethesda IV, 50%-35%; Bethesda V, 93%-91%; and Bethesda VI, 99%-98%. Absolute ROM differences for each category were as follows: Bethesda I, 0%; Bethesda II, 4%; Bethesda III, 7%; Bethesda IV, 15%; Bethesda V, 2%; and Bethesda VI, 1%.

CONCLUSIONS

A decreasing trend in absolute and relative ROM was seen in Bethesda II, III, and IV categories; however, exclusion of NIFTP as a malignant lesion did not significantly alter the ROM of BSRTC categories. Surgeons should assess their respective institution's experiences with NIFTP and the BSRTC.

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.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features and the risk of malignancy in The Bethesda System for the Reporting of Thyroid Cytopathology

INTRODUCTION

The Bethesda System for the Reporting of Thyroid Cytopathology (TBSRTC) is used to categorize and diagnose thyroid nodules by fine needle aspiration biopsy (FNAB). Each category in TBSRTC is associated with an estimated risk of malignancy (ROM). A subset of noninvasive encapsulated follicular variant of papillary thyroid carcinoma (niEFVPTC) was reclassified as a nonmalignant tumor: noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). We studied the impact of this reclassification on the reported ROM in TBSRTC.

MATERIAL AND METHODS

We searched our institutional files for thyroid FNAB with surgical follow-up. ROM for each TBSRTC category was calculated. Subsequently, cases of niEFVPTC were reviewed and reclassified as NIFTP, if appropriate. ROM for each category was then recalculated after the reclassification.

RESULTS

Twenty-six NIFTP were identified; the corresponding FNABs were distributed among all six TBSRTC categories. The majority of NIFTP FNAB were in the AUS/FLUS and suspicious for malignancy (SUSP) categories, 12 (46.2%) and 8 (30.8%), respectively. While the ROM changed for all diagnostic categories, the greatest change in ROM after reclassification was seen in these two categories. Absolute ROM for AUS/FLUS decreased from 25.0% to 21.0% and SUSP, from 71.7% to 58.3%, changes that were statistically significant.

CONCLUSIONS

The reclassification of niEFVPTC to NIFTP has significantly impacted the ROM in the TBSRTC at our institution. While there was a decrease in ROM for all categories, the greatest reduction to ROM was in the categories of AUS/FLUS and FN. These changes to the ROM should help guide surgical approach moving forward.

A 15 year institutional experience of well-differentiated follicular cell-derived thyroid carcinomas; impact of the new 2017 TNM and WHO Classifications of Tumors of Endocrine Organs on the epidemiological trends and pathological characteristics

PURPOSE

Our study aimed to describe the evolution of the rate of pathological subtypes of well-differentiated follicular-cell derived thyroid carcinomas (DTCs) in the Department of Pathology, Emergency County Hospital Targu-Mures, Romania over a 15 year period and to assess the impact the new 2017 WHO and TNM classifications of thyroid tumors had on our cases.

METHODS

The pathological data were retrieved from the original pathological reports. After applying the exclusion criteria the remaining cases were reviewed on a double-headed microscope and reclassified according to the 2017 WHO and TNM staging system. The follow-up data were collected from the Institute of Oncology Cluj-Napoca, Romania.

RESULTS

Our study included 396 cases of DTCs (375 papillary, 11 follicular, and 10 Hürthle cell carcinomas). PTCs revealed a significant increasing trend over the study period, whereas follicular and Hurthle cell carcinomas remain rare; 125/131 of noninvasive encapsulated follicular variant PTC (EFVPTC) were reclassified as noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTPs), resulting in a 33.3% reduction in the number of PTCs. According to 2017 TNM stage-grouping 31% of 271 patients with DTC were downstaged. Follow-up data were available for most of the patients (65.7%, mean period 58.1 months). All patients with noninvasive EFVPTC were disease free at the last clinical assessment.

CONCLUSIONS

The increasing rate of PTC was maintained even after exclusion of NIFTP. By applying 2017 TNM criteria, a significant number of DTC cases were downstaged into a more favorable group. Follow-up data highlight the indolent behavior of noninvasive EFVPTCs reclassified as NIFTPs.

Can cytology and the Thyroid Imaging, Reporting, and Data System (TI-RADS) identify noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) before surgery?

INTRODUCTION

In 2017, the American College of Radiology (ACR) created the Thyroid Imaging, Reporting, and Data System (TI-RADS) to select thyroid nodules for fine-needle aspiration (FNA). The objective of this study is to find out whether ACR TI-RADS is useful in triaging thyroid follicular cells with papillary-like nuclear features obtained by FNA to determine the extent of surgery.

MATERIAL AND METHODS

The grayscale ultrasound of 76 noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), 41 encapsulated (E), and 79 infiltrative (I) follicular variant (FV) of papillary thyroid carcinoma (PTC) were reviewed and assigned TI-RADS points and then suspicion levels.

RESULTS

Of the 39 tumors with high suspicion level, 32 were IFVPTC, and seven were EFVPTC. Of the 137 tumors with moderate suspicion level, 47 were IFVPTC, 34 were EFVPTC, and 56 were NIFTP. Of the 19 tumors with mild suspicion level, all were NIFTP. The only tumor with no suspicion was an NIFTP. IFVPTC had a significantly higher suspicion level than EFVPTC and NIFTP (P < 0.0001). The difference in suspicion level between EFVPTC and NIFTP is not statistically significant. None of the cases of NIFTP in the study had a high suspicion level.

CONCLUSIONS

The study demonstrates that cytology interpreted in the context of ACR TI-RADS suspicion levels can separate NIFTP from many IFVPTC and a few EFVPTC with overt invasion. PTC could be diagnosed in cytology if cells with papillary-like nuclear features derived from TR5 nodules. The nodules with TR4 or less that yield similar cells require surgical pathology to diagnose FVPTC with microscopic capsular or vascular invasions.

Comprehensive DNA Methylation Profiling Identifies Novel Diagnostic Biomarkers for Thyroid Cancer

Background: There are no reliable biomarkers to accurately differentiate indolent thyroid tumors from more aggressive thyroid cancers. This study aimed to develop new DNA methylation markers for diagnosis and recurrence risk stratification of papillary thyroid carcinoma (PTC). Methods: Thyroid tumor-specific DNA methylation profiling was investigated in 34 fresh frozen tissues, which included nontumor (n = 7), noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP, n = 6) and PTC (n = 21), using the Illumina HumanMethylation EPIC array. We performed a genome-wide assessment of thyroid tumor-specific differentially methylated CpG sites in the discovery set, then validated the top candidate markers in an independent set of 293 paraffin tissue samples comprised of follicular adenoma (FA, n = 61), Hürthle cell adenoma (HA, n = 24), NIFTP (n = 56), PTC (n = 120), follicular thyroid carcinoma (n = 27), and Hürthle cell carcinoma (n = 5), by pyrosequencing. Results: Three selected markers (cg10705422, cg17707274, and cg26849382) differentiated nonmalignant (FA, HA, and NIFTP) tumors from differentiated thyroid cancers with area under the receiver operating characteristic curve of 0.83, 0.83, and 0.80, respectively. Low DNA methylation levels for three markers were significantly associated with recurrent or persistent disease (odds ratio (OR) = 3.860 [95% confidence interval (CI) 1.194-12.475]) and distant metastasis (OR = 4.009 [CI 1.098-14.632]) in patients with differentiated thyroid cancer. A subgroup analysis for the validation set showed that PTC patients with low DNA methylation levels more frequently had aggressive histology, extrathyroidal extension, lymph node metastasis, BRAF^V600E mutations, and recurrent or persistent disease than those with high levels of methylation markers. All PTC patients who developed disease recurrence had low DNA methylation levels for three markers. Conclusions: DNA methylation levels of three markers can be useful for differentiating differentiated thyroid cancer from nonmalignant follicular thyroid lesions, and may serve as prognostic biomarkers for predicting recurrent or persistent disease after surgery for differentiated thyroid cancer.

Long-term progression of non-invasive follicular thyroid neoplasm with papillary-like nuclear features: A single-center retrospective study of the French Marne-Ardennes thyroid cancer registry

CONTEXT

Non-invasive forms of encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) were reclassified as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in order to reduce overtreatment. A few studies showed neck lymphadenopathy at diagnosis, or even distant metastasis in patients with NIFTP.

OBJECTIVE

Our aim was to report the frequency, clinical features and long-term progression of histologically confirmed NIFTP, using data from the French Marne-Ardennes thyroid cancer registry, and to compare findings against FVPTC.

METHODS

This was a retrospective study on data for follicular variant of PTC (FVPTC) diagnosed between 1975 and 2015 obtained from the specialized Marne-Ardennes thyroid cancer registry. Pathology reports were used to select appropriate cases from a large series, and FVPTC specimens were reviewed by endocrine pathologists. Strict diagnostic criteria were used for reclassification as NIFTP.

RESULTS

In total, 115 cases were reviewed histologically out of 383 cases of FVPTC. Sixty-five met all criteria for NIFTP and were consequently reclassified. Incidence of NIFTP was 16.9% of cases of FVPTC. Fifty patients were women (76.9%); median age was 47 years. Mean NIFTP size was 2.6 cm. There were no significant differences in age, gender or tumor size between NIFTP and FVPTC. Fifty patients underwent total thyroidectomy and 15 lobectomy. There were no lymph node metastases at diagnosis, and none of the patients (N=17) who underwent central and/or lateral neck dissection had positive findings on microscopic examination. 46 patients (70.8%) received radioiodine (RAI). Patients were followed up for 1.9-27.3 years (median 14.6 years) after initial treatment. All patients remained in complete remission during follow-up.

CONCLUSION

Consistently with previous studies, our results showed the indolent course of NIFTP and that risk of recurrence after complete resection is very low (zero in our cohort), even when size is ≥4cm and in absence of adjuvant RAI treatment. Prospective studies are needed to confirm those results.

Preoperative prediction of non-invasive follicular thyroid neoplasm with papillary-like nuclear features: a Canadian single-Centre experience

Background

An international group of experts recommended reclassifying non-invasive follicular variant of papillary thyroid cancers (FVPTC) as ‘non-invasive follicular thyroid neoplasm with papillary-like nuclear features’ (NIFTP) in April 2016. The purpose of this study was to establish preoperative clinical, laboratory, ultrasonographic, and cytological variables, which can differentiate NIFTP from FVPTC.

Methods

We conducted a retrospective chart review of consecutive patients from a single institution evaluated between January 2012 and December 2017. 203 adult patients underwent lobectomy or total thyroidectomy for a FVPTC during that period. Each patient’s medical chart was reviewed and information on pre-operative variables was recorded. An expert pathologist reviewed all surgical specimens and reclassified a subset of FVPTC as NIFTP according to the specific criteria.

Results

Overall, 44 patients were included in the NIFTP group and 159 in the non-NIFTP group. Mean age was 50.1 years in the NIFTP group and 50.7 in the non-NIFTP group. Most patients were female (86.4% (38/44) in the NIFTP group vs 79.8% (127/159) in the non-NIFTP group). More patients underwent lobectomy in the NIFTP group (50% (22/44) vs 16.4% (26/159) in the non-NIFTP group, p = < 0.0001). Less patients received radioactive iodine in the NIFTP group (31.8% (14/44) vs 52.2% (83/159) in the non-NIFTP group, p = 0.0177). Preoperative thyroglobulin levels were lower in NIFTP patients (Median 25.55 mcg/L +/− 67.8 vs 76.06 mcg/L +/− 119.8 in Non-NIFTP, p = 0.0104). NIFTP nodules were smaller (Mean size 22.97 mm +/− 12.3 vs 25.88 mm +/− 11.2 for non-NIFTP, p = 0.0448) and more often solid than non-NIFTP (93.2% (41/44) vs 74.8% (119/159) for non-NIFTP, p = 0.0067). 2017 ACR TIRADS nodule category of 1–4 on ultrasound had a negative predictive value and a sensitivity of 100% for NIFTP. ROC Curve Analysis demonstrated that a preoperative thyroglobulin level of 31.3 mcg/L had a sensitivity of 75% and a specificity of 62.5% to differentiate NIFTP from non-NIFTP cancers.

Conclusion

Lower preoperative thyroglobulin levels, smaller nodule size, solid texture and 2017 ACR TIRADS Category of 1–4 are more strongly associated with NIFTP than FVPTC and can favour less invasive surgical options such as lobectomy.

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC): A report of 2,781 cases in a Chinese population

Objective

To evaluate the diagnostic utility of The Bethesda System for Reporting Thyroid Cytology (TBSRTC) at Peking University Cancer Hospital, the incidence of noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP), and the impact of reclassification on cytopathological outcomes.

Methods

We performed a retrospective study of thyroid fine-needle aspiration (FNA) cases between April 2014 and March 2019. The FNA results were classified according to TBSRTC. Post-surgery histological findings were followed up.

Results

A total of 2,781 thyroid FNAs were performed. The incidences of the 6 diagnostic categories (DCs I-VI) were 14.8%, 17.1%, 15.8%, 2.3%, 11.6% and 38.5%, respectively. A total of 1,122 patients (40.3%) had corresponding histological results. NIFTP accounted for 0.4% of papillary thyroid carcinoma (PTC) cases, and there was no significant difference in the risk of malignancy (ROM) for each TBSRTC DC between "NIFTP=carcinoma (Ca)" and "NIFTP≠Ca". When "NIFTP=Ca", the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of TBSRTC were 98.0%, 84.0%, 99.4%, 58.3%, and 97.5%, respectively. When "NIFTP≠Ca", the sensitivity, specificity, PPV, NPV and accuracy of the TBSRTC were 98.1%, 81.5%, 99.3%, 61.1%, and 97.5%, respectively.

Conclusions

TBSRTC is effective in the preoperative diagnosis of thyroid nodules in Peking University Cancer Hospital. The impact of the reclassification of NIFTP on cytopathological outcomes is limited because of its low incidence, and the revised ROMs are not suitable for Asian patients.

Differences in surgical resection rate and risk of malignancy in thyroid cytopathology practice between Western and Asian countries: A systematic review and meta-analysis

There is increasing evidence showing that clinicians employ different management strategies in their use of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC). In this meta-analysis, we investigated the differences in diagnosis frequency, resection rate (RR), and risk of malignancy (ROM) between Western (ie, American and European) and Asian cytopathology practices. We searched PubMed and Web of Science from January 2010 to January 2019. Proportion and 95% CIs were calculated using a random-effect model. We used independent sample t tests to compare frequencies, RR, and ROM between Western and Asian practices. We analyzed a total of 38 studies with 145,066 fine-needle aspirations. Compared with Asian practice, Western series had a significantly lower ROM in most of TBSRTC categories, whereas the RR was not statistically different. Focusing on indeterminate nodules, the RR in Western series was significantly higher (51.3% vs 37.6%; P = .048), whereas the ROM was significantly lower (25.4% vs 41.9%; P = .002) compared with those in Asian series. The addition of Asian cohorts increased ROM for most of diagnostic categories compared with the original TBSRTC. In conclusion, this study demonstrates a difference in Western and Asian thyroid cytology practice, especially regarding the indeterminate categories. Lower RR and higher ROM suggest that Asian clinicians adopt a more conservative approach, whereas immediate diagnostic surgery is favored in Western practice for indeterminate nodules. The addition of Asian series into a meta-analysis of TBSRTC altered ROM for several categories, which should be considered in future revisions of TBSRTC.

Noninvasive follicular neoplasm with papillary like nuclear features: A comprehensive analysis with a diagnostic algorithm

BACKGROUND

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) lacks the carcinoma label, avoiding aggressive therapy, physiological, social and financial impact of cancer diagnosis. Unfortunately, the preoperative diagnosis is still a challenge. Varied incidence of NIFTP has been document with limited data on preoperative cytological, radiological characteristics and the impact on risk of malignancy in each category of the Bethesda system of reporting thyroid cytopathology.

METHOD

Retrospective analysis of 20 NIFTPs with an attempt to provide a preoperative diagnostic algorithm based on the cytological and ultrasound features along with incidence and implication on risk of malignancy in various Bethesda categories with its impact on patient management.

RESULT

Incidence of NIFTP in our study was higher in comparison to that documented from other Asian countries. TIRADS 3 was the most common sonographic diagnosis. NIFTP was commonly preceded by indeterminate or benign Bethesda category. Major impact of excluding NIFTP form malignant category was seen on Bethesda categories II and IV with 20% and 27% reduction in risk of malignancy, respectively.

CONCLUSION

Retrospective analysis should not be confined only to follicular variant of papillary thyroid carcinoma but cases of follicular adenoma and adenomatous colloid nodule should always be included in review to ascertain the true incidence of NIFTP. NIFTPs are less likely to have malignant preoperative cytology. NIFTP shares major cytological and ultrasound features with follicular adenoma, adenomatous colloid nodule and minimally invasive follicular papillary carcinoma. When analyzed together, taking minor findings in consideration, can favor a diagnosis.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is rare, benign lesion using modified stringent diagnostic criteria: Reclassification and outcome study

BACKGROUND

Rigid diagnostic criteria for NIFTP have been recently proposed. The frequency of NIFTP using the new criteria is unknown, and whether abortive papillae are associated with BRAF^V600E mutation has not been studied. The aim of this study is to identify NIFTP by a retrospective review of Follicular Variant of Papillary Thyroid Carcinoma (FVPTC), and to study its incidence as well as the association between immunohistochemical BRAF^V600E expression and abortive papillae in NIFTP.

DESIGN

Thyroid tumors diagnosed as FVPTC or NIFTP over a period of 18 years (2000-2017) were identified using the laboratory information system. The final pathology reports were reviewed and potential NIFTP were retrieved. The archived slides for these cases were independently reviewed by 2 pathologists. BRAF^V600E (clone: VE1) immunostain was performed on representative tumor blocks. Clinical information including follow-up data was obtained from the electronic medical records.

RESULTS

Among the 1918 cases with the diagnosis of papillary thyroid carcinoma (PTC), 589 (30.7%) of FVPTC and 136 cases of potential NIFTP were identified. After the review of the archived pathology slides, 29 lesions were morphologically reclassified as NIFTP. Four (13.7%) of these were positive for BRAF^V600E; no association was found between the presence of abortive papillae and BRAF^V600Eexpression (p=0.3). Exclusion of the 4 cases with BRAF^V600Eexpression resulted in 25 lesions of final NIFTP, representing 4.2% of the FVPTC and 1.3% of the PTC. The mean age of the NIFTP patients was 50 years, 87.5% were females. The mean size of the lesions was 1.4 cm (0.1-4.0 cm). Intranuclear pseudoinclusions were not identified, and abortive papillae were identified in 60% of NIFTP. The average follow-up was 70 (28-166) months. There were no adverse events (recurrence or metastasis) in the NIFTP group.

CONCLUSION

When strictly defined, NIFTP comprises 1.3% of cases perviously classified as PTC. In morphological NIFTP, no correlation is found between the presence of abortive papillae and the BRAF^V600E expression. Intranuclear pseudo-inclusions are not observed in NIFTP. Modification of current morphological criteria to include BRAF^V600E immunohistochemistry test may stratify NIFTP with benign outcome.

Thyroid Tumors You Don't Want to Miss

This article examines more uncommon thyroid entities, including anaplastic thyroid carcinoma, poorly differentiated thyroid carcinoma, rare papillary thyroid carcinoma variants, medullary thyroid carcinoma, non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), and multiple adenomatous nodules in the setting of Cowden syndrome. These entities were chosen based on their clinical significance and because they can be diagnostically challenging due to their morphologic diversity and overlap with other thyroid tumors. This article addresses the diagnostic features of each entity, focusing on how to avoid potential pitfalls and mimics while also highlighting the clinical implications of each diagnosis.

Characterization of thyroid cancer driven by known and novel ALK fusions

ALK fusions are found in various tumors, including thyroid cancer, and serve as a diagnostic marker and therapeutic target. Spectrum and outcomes of ALK fusions found in thyroid nodules and cancer are not fully characterized. We report a series of 44 ALK-translocated thyroid neoplasms, including 31 identified preoperatively in thyroid fine-needle aspirates (FNA). The average patients' age was 43 years (range, 8-76 years); only one with radiation history. All 19 resected thyroid nodules with ALK fusion identified preoperatively were malignant. Among nodules with known surgical pathology (n = 32), 84% were papillary thyroid carcinomas (PTCs) and 16% poorly differentiated thyroid carcinomas (PDTCs). PTCs showed infiltrative growth with follicular architecture seen exclusively (30%) or in combination with papillary and/or solid growth (37%). Tumor multifocality was seen in 10 (31%) PTC cases. Most PDTC had a well-differentiated PTC component. Lymph node metastases were identified in 10/18 (56%) patients with neck dissection. The most common ALK fusion partners were STRN (n = 22) and EML4 (n = 17). In five cases, novel ALK fusion partners were discovered. All five PDTCs carried STRN-ALK fusion. On follow-up, ten patients were free of disease at 2-108 months, whereas two patients with PDTC died of disease. In summary, ALK fusion-positive thyroid carcinomas are typically infiltrative PTC with common follicular growth, which may show tumor dedifferentiation associated with increased mortality. Compared to EML4-ALK, STRN-ALK may be more common in PDTC, and ~10% of ALK fusions occur to rare gene partners. When ALK fusion is detected preoperatively in FNA samples, malignancy should be expected.

Revised criteria for diagnosis of NIFTP reveals a better correlation with tumor biological behavior

The recent reclassification of a follicular variant of papillary thyroid carcinoma (FVPTC), subset as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), aims to avoid overtreatment of patients with an indolent lesion. The diagnosis of NIFTP has recently been revisited using more rigid criteria. This study presents histological and molecular findings and a long clinical follow-up of 94 FVPTC, 40 cases of follicular adenoma (FTA) and 22 cases of follicular carcinoma (FTC) that were classified before the advent of the NIFTP reclassification. All slides were reviewed using these rigid criteria and analysis of numerous sections of paraffin blocks and reclassified as 7 NIFTPs, 2 EFVPTCs, 29 infiltrative FVPTC (IFVPTCs), 57 invasive EFVPTC (I-EFVPTCs), 39 FTAs and 22 FTCs. Remarkably, EFVPTC and NIFTP patients were all free of disease at the end of follow-up and showed no BRAF mutation. Only one NIFTP sample harbored mutations, an NRAS Q61R. PAX8/PPARG fusion was found in I-EFVPTCs and FTC. Although additional studies are needed to identify a specific molecular profile to aid in the diagnosis of lesions with borderline morphological characteristics, we confirmed that the BRAF V600E mutation is an important tool to exclude the diagnosis of NIFTP. We also show that rigorous histopathological criteria should be strongly followed to avoid missing lesions in which more aggressive behavior is present, mainly via the analysis of capsule or vascular invasion and the presence of papillary structures.

Fifty years of thyroid pathology: concepts and developments

The past half century has seen a number of advances in pathology of thyroid diseases, especially neoplastic lesions. These include the description of new entities, the definition of prognostically important lesions, the incorporation of fine needle aspiration biopsy and its functional risk stratification of diagnoses into the clinical evaluation and therapeutic recommendations of the patient with thyroid nodules and the understanding of thyroid neoplastic development, diagnostic and prognostic parameters by use of molecular analysis so that such techniques are becoming standard of care for patients with thyroid tumors. The histopathologist and cytopathologist have been and continue to be at the forefront in the definition and understanding of these areas of thyroid disease. This review describes many of the most important advances in this area in an attempt bring the practicing pathologist up to date in these developments.

Colon Cancer Metastasis Within a NIFTP: A Case Report and Review of the Literature

The thyroid is an unusual site for metastasis, and metastases in a preexisting primary thyroid tumor are exceedingly rare. We report the first case of a patient with colon cancer who was diagnosed with a thyroid metastasis in a noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). A 55-year-old male patient presented with a 19 mm thyroid nodule in the inferior left lobe. It was EU-TIRADS 5 on echography and suspicious of papillary thyroid carcinoma (Bethesda V) on cytology. Macroscopically, the nodule was fleshy and completely encapsulated. At frozen section examination, it demonstrated follicular architecture with mild atypia. Inside the nodule was a focus of tumor with glandular architecture, marked cellular atypia, and necrosis. These findings suggested a secondary malignancy. The patient's medical history was significant for metastatic colon cancer. The definitive histology showed features of metastatic colorectal adenocarcinoma within a NIFTP. Immunohistochemical studies were confirmatory with expression of CDX2 and CK20 localized to the metastatic focus. PAX8, TG, and TTF were negative in the metastasis but expressed in the surrounding NIFTP lesion. The possibility of a metastasis to the thyroid may be considered in patients presenting with a solitary thyroid nodule with a previous history of cancer. Metastatic colorectal adenocarcinoma occurring in a NIFTP has never been reported before now, although metastases to the thyroid are documented in the literature. In cases of a secondary malignancy to the thyroid, treatment is controversial.

Systematic Review and Meta-analysis of the Impact of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP) on Cytological Diagnosis and Thyroid Cancer Prevalence

A re-named diagnosis of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) likely impacts the prevalence of thyroid cancer and risk of malignancy in populations based on the established Bethesda System of Reporting Thyroid Cytopathology (TBSRTC). This study was done to investigate the prevalence and cytological distribution of NIFTP. PRISMA guided systematic review was done from a database search of Pubmed, EMBASE, and Medline using the search terms "non-invasive follicular thyroid neoplasm with papillary-like nuclear features", "non-invasive follicular variant of papillary carcinoma", "niftp", and "Bethesda" until November 2018. Original articles with surgically proven diagnoses of NIFTP using strict NIFTP criteria were included. Twenty-nine studies with 1563 cases of NIFTP were included. The pooled prevalence of NIFTP in cases which would be classified previously as the follicular variant of papillary thyroid cancer (FVPTC) and papillary thyroid cancer (PTC) were 43.5% (95% CI 33.5-54.0%) and 4.4% (95% CI 2.0-9.0%) respectively. The pooled TBSRTC distribution of cases diagnosed as NIFTP was: from the non-diagnostic category 3.6% (95% CI 2.4-5.3%), benign 10.0% (95% CI 7.2-13.6%), AUS/FLUS 34.2% (95% CI 28.2-40.8%), FN/SFN 22.7% (95% CI 17.2-29.4%), suspicious for malignancy 22.4% (95% CI 17.7-27.9%), and malignant 7.5% (95% CI 4.2-12.9%). While a significant reduction in FVPTC prevalence is anticipated, a modest reduction of PTC prevalence is also expected with adoption of the NIFTP terminology that would be distributed mainly among lesions classified as indeterminate thyroid nodules. Further studies are needed to identify unique clinical characteristics of these lesions preoperatively.

Peptide Profile Differences of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features, Encapsulated Follicular Variant, and Classical Papillary Thyroid Carcinoma: An Application of Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging

Introduction: The lack of papillary structures and faint and/or unclear core features of follicular variant of papillary thyroid carcinoma (FV-PTC) may hamper the definitive fine needle aspiration biopsy -based diagnosis. Recently, the nomenclature of noninvasive encapsulated FV-PTC was revised to "noninvasive follicular thyroid neoplasms with papillary-like nuclear features" (NIFTP). However, it remains inconclusive whether or not the peptide patterns differ between NIFTP and encapsulated FV-PTC. The main objectives of this study were to investigate the viability of matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) in the pathological assessment of NIFTP and to evaluate the discriminatory power of MALDI MSI for the classification of classical variant of PTC (CV-PTC), NIFTP, and encapsulated FV-PTC. Methods: MALDI MSI was employed to investigate the changes in peptide profiles from 21 formalin-fixed paraffin-embedded (FFPE) tissue samples (n = 7 from each group of CV-PTC, NIFTP, and FV-PTC). Six out of seven FV-PTC FFPE tissue samples were encapsulated FV-PTC; only one was infiltrative FV-PTC. Liquid chromatography-tandem mass spectrometry was used for the identification of the peptide signals detected in MALDI MSI. Results: Using receiver operating characteristics analysis, 10 peptide signals distinguished NIFTP from normal thyroid parenchyma (area under the curve [AUC] >0.80). To evaluate the discriminatory power of MALDI MSI, statistically significant peptide signals (n = 88) within three groups were used for hierarchical clustering. The method had high discriminatory power for distinguishing CV-PTC from NIFTP and FV-PTC (encapsulated and infiltrative). The majority of the NIFTP and encapsulated FV-PTC were clustered together, indicating that NIFTP could not be distinguished from encapsulated FV-PTC. However, infiltrative FV-PTC FFPE tissue samples had the furthest distance from all the NIFTP cases. High signal intensities of S100-A6, vimentin, and cytoplasmic actin 1 were detected in FV-PTC, prelamin A/C in CV-PTC, and 60S ribosomal protein L6 and L8 in NIFTP tissues. Conclusions: MALDI MSI, a powerful tool combining histological and mass spectrometric data, enabled the differentiation of NIFTP from normal thyroid parenchyma. Although NIFTP is a recent definition that replaces noninvasive encapsulated FV-PTC, the peptide profiles of NIFTP and encapsulated FV-PTC were found to be similar.

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP): Update and Diagnostic Considerations-a Review

Advances in our understanding of thyroid lesions, especially those entities with an indolent behavior, has led clinicians to question the most appropriate surgical management of such thyroid nodules. Several studies have shown that the non-invasive encapsulated follicular variant of papillary thyroid carcinomas (NI-EFVPC) exhibits poor histopathologic diagnostic reproducibility and have been over-treated as conventional thyroid cancer. In 2015, an international thyroid working group re-evaluated NI-EFVPC and its diagnostic criteria. The new terminology of "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) was accordingly introduced to replace NI-EFVPC. The literature has emphasized that NIFTPs are biologically similar to follicular adenomas lacking lymph node metastases and/or recurrence. While the definition of NIFTP is based on specific morphological parameters, recent studies have questioned whether the criterion allowing less than 1% of true papillae should be revised to a total absence of papillae. The motivation for this revision is the rare finding, in some studies, of lymph nodes with metastatic NIFTP. This review evaluates the existing published series of NIFTP cases, clinical consequences of NIFTP, and emerging changes in the diagnostic criteria for NIFTP. The introduction of NIFTP has resulted in significant impact on the clinical management of thyroid nodules. Recent revisions in the morphological criteria for NIFTP emphasize the need to adhere to very stringent histomorphologic criteria when making a diagnosis of NIFTP. The adoption of NIFTP terminology instead of NI-EFVPC is associated with conservative lobectomy without radioactive iodine treatment in the majority of cases.

Non-invasive follicular thyroid neoplasm with papillary-like nuclearfeatures (NIFTP): a review and update

BACKGROUND

The nomenclature "Non-invasive Follicular Neoplasm with Papillary-like Nuclear Features (NIFTP)" was introduced in 2016. While NIFTP differs from classic papillary thyroid carcinoma (PTC) in imaging, cytomorphology, histology, molecular profile, treatment, follow up, outcome, and behavior, it largely overlaps with follicular variant of PTC at imaging and cytomorphology. Herein, we review the literature for better understanding NIFTP, and its impact on patient care.

METHODS

The English literature was thoroughly evaluated with the key word of "Noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP)".

OBSERVATIONS

NIFTP presents as a thyroid nodule. On imaging, it is a round-to-oval, well circumscribed mass with solid internal content. Aspirated material shows a microfollicular pattern with focal nuclear features of PTC mostly reported in categories 3-5 of the Bethesda System for Reporting Thyroid Cytology (TBRSTC). NIFTP has decreased risk of malignancy in TBRSTC categories 3-6. Histologic examination of NIFTP reveals an encapsulated neoplasm with follicular pattern and nuclear features of PTC with no capsular or vascular invasion. No papillary structure, atypia, or mitosis is present. In contrast to PTC, only 4% of NIFTP cases harbor a BRAF mutation. Because NIFTP carries an excellent prognosis and indolent behavior, the tumor behavior was changed from malignant to a neoplasm with tumor with extremely indolent behavior. The recommended treatment is lobectomy with no further ablation therapy. Until better understanding of NIFTP, patient's follow up should be occasionally performed by neck ultrasonography and serum thyroglobulin measurement.

CONCLUSION

NIFTP carries an excellent prognosis. It is critical for both clinicians and patients to be aware of extremely indolent behavior of NIFTP in order to prevent unnecessary, aggressive treatment.

Incidence of noninvasive follicular thyroid neoplasm with papillary-like nuclear features and change in risk of malignancy for "The Bethesda System for Reporting Thyroid Cytology"

INTRODUCTION

The second edition of The Bethesda System for Reporting Thyroid Cytopathology has incorporated the recent change in nomenclature, noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), with an anticipated change in the risk of malignancy (ROM). We examined our institutional experience in the incidence of NIFTP and the change in the ROM in The Bethesda System for Reporting Thyroid Cytopathology.

MATERIALS AND METHODS

A computerized search was performed from January 2013 to August 2017 for all thyroid fine needle aspirations (FNAs), the corresponding surgical resection specimens, and clinical follow-up data. All thyroid specimens reported as follicular variant of papillary thyroid carcinoma were reviewed and reclassified, and all NIFTP diagnoses from April 2016 to August 2017 were identified. The ROM for each category was calculated before and after the change and analyzed for significance.

RESULTS

A total of 4500 thyroid FNA cases were collected. Of these, 479 cases had surgical resection specimens available and 36 cases had been diagnosed as NIFTP. Of these, 22 had been previously diagnosed as FVPT. Of 27 cases of NIFTP, 14 and 13 were atypia of undetermined significance/follicular lesion of undetermined significance and follicular neoplasm/suspicious for follicular neoplasm, respectively. A reduction in the ROM was observed in these 2 categories (P = 0.03 and P = 0.04, respectively).

CONCLUSIONS

In our institution, NIFTP has accounted for 13% of all malignant thyroid neoplasms since the change in nomenclature. Although the ROM was decreased in the affected categories, with absolute statistically significant decreases in ROM of 15% and 16.2% for category III and IV, respectively, the overall ROM change was marginal.

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features is Rare: A Population Based Study of Incidence

The renaming of encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) to noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was proposed by a group of experts in 2016 to prevent overtreatment of indolent, low-risk thyroid cancers. The aim of this study was to estimate the incidence and outcome for patients meeting the NIFTP criteria in a well-defined geographic region. Our cohort consisted of 134 patients with papillary thyroid carcinoma from the Region of Southern Denmark (RSD), 2007 to 2011. Patients were retrieved from the Danish Thyroid Cancer (DATHYRCA) Database. All potential NIFTP cases were reviewed by a thyroid pathologist. We identified no cases meeting all diagnostic criteria, but one probable NIFTP case from 2007 to 2011. The patient was treated according to the national guidelines and is alive and recurrence-free after 106 months of follow-up. Molecular testing showed KRAS mutation. In a population based set up the incidence rate of NIFTP is very low.

BRAF mutation in cytologically indeterminate thyroid nodules: after reclassification of a variant thyroid carcinoma

Purpose

Fine-needle aspiration biopsy (FNAB) is regarded by the Bethesda system as the gold-standard investigation for stratifying the risk of malignancy of a thyroid nodule. However, some limitations affect the adequacy of the obtained materials, resulting in 30% of the cytological results remaining in the indeterminate category. We aimed to investigate the diagnostic value of the BRAF mutation in cytologically indeterminate thyroid nodules after the reclassification of a variant thyroid carcinoma.

Patients and methods

In this prospective diagnostic study, 76 patients with FNAB findings of atypia of undetermined significance (AUS) and suspicious for malignancy (SUS) were included. The BRAF V600 mutation from FNAB was confirmed by a PCR-based method (Sanger sequencing combined with allele-specific real-time PCR techniques) and immunohistochemistry (IHC). Pathological specimens and features, including noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), were reviewed and compared to the FNAB results.

Results

Using the PCR-based method, the BRAF mutation was positive in 13/76 cases (17.1%), with the diagnostic values of 16.7% sensitivity, 100% specificity, 100% positive predictive value (PPV), and 82.8% negative predictive value (NPV) in the AUS compared to 73.3% sensitivity, 100% specificity, 100% PPV, and 20% NPV in the SUS. For the IHC technique, only 20 of the 76 cytological specimens were qualified for testing. The BRAF mutation was positive in 13/20 cases, with the diagnostic values of 100% sensitivity, 63.6% specificity, 42.9% PPV, and 100% NPV in the AUS compared to 100% sensitivity and PPV in the SUS. The BRAF mutation was not found in the pathological reports for NIFTP.

Conclusion

The malignancy rate is high in our data, with specific and acceptable accuracy rates for the BRAF mutation from FNAB found by using the PCR-based method. NIFTP has been introduced after the pathological reclassification. Molecular diagnosis might be useful to establish the nature of the disease.