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

Detailed fine needle aspiration cytopathology findings of noninvasive follicular thyroid neoplasm with papillary-like nuclear features with nuclear grading correlated to that of biopsy and Bethesda category and systematic review

BACKGROUND

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) poses diagnostic challenge in fine needle aspiration cytopathology (FNAC). We aimed first to document our FNAC Bethesda categories (BCs) for all of our NIFTPs and compare our findings with those in the literature with series containing at least 14 cases each.

METHODS

Cases with final histopathological diagnoses of NIFTP and their preoperative FNAC were retrieved from 2006 to 2022 and our cytopathological BCs were documented. Then the slides were re-reviewed in a blinded manner for detailed classification and the results of both the BCs and blinded reclassification were compared with series in the literature for both BCs and detailed cytopathological review of the cases.

RESULTS

Thyroid FNACs of 43 out of 86 patients with final NIFTP diagnoses were obtained. Females composed 72.1% (F/M: 31/12); mean age and mean tumor diameter was 47.6 (19-72 years) and 23.4 mm (7-60 mm), respectively. Totally 81.4% (35/43) were classified in the "indeterminate" diagnostic categories; namely 44.2% (19/43) were reported as atypia of undetermined significance (AUS; BC III), 20.9% (9/43) were follicular neoplasm (FN; BC IV), and 16.3% (7/43) were suspicious for malignancy (SM; BC V). No patient was diagnosed as positive for malignancy (BC VI), preoperatively. Detailed cytomorphologic reevaluation revealed heterogeneous cytopathologic findings and nuclear grade (especially nuclear enlargement, membrane irregularity and elongation) significantly increased with respect to BCs. Systematic review confirmed extremely heterogeneous cytomorphologic nature of NIFTP.

CONCLUSIONS

NIFTPs were categorized most frequently as AUS, followed by FN and SM on FNAC. Our re-review were not able to specify features solely unique to NIFTP alone but may distinguish these cases from classic papillary thyroid carcinoma.

An investigation into noninvasive follicular thyroid neoplasms with papillary-like nuclear features: does the initial proposal on noninvasive follicular thyroid neoplasms with papillary-like nuclear features behavior hold true?

Current management of patients with noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP) is lobectomy with close clinical follow-up. Because this entity is still young, we present our 5-year institutional experience with NIFTP since that time. Cases of NIFTP diagnosed from 2017 to 2022 were identified. Data points including patient demographics, radiology, cytologic and pathologic diagnoses, molecular profiles, and clinical follow-up were documented. A literature review of NIFTP case series was performed. A total of 379 cases were included (mean age: 52 years, female:male ratio 3.3:1). Ultrasound findings were available for 260 patients, and 247 underwent fine-needle aspiration (FNA). The FNA diagnoses per the Bethesda System for Reporting Thyroid Cytology were nondiagnostic (n = 2), benign (n = 16), atypia of undetermined significance/follicular lesion of undetermined significance (n = 119), follicular neoplasm/suspicious for follicular neoplasm (n = 68), suspicious for malignancy (n = 31), and malignant (n = 11). Molecular testing was performed in 179 cases. Lobectomy was performed for 183, total thyroidectomy for 192, and nodulectomy for 4 cases. The average size of NIFTP was 2.3 cm, and 232 cases had additional nodules (including benign and malignant neoplasms). Multifocal NIFTP occurred in 32 patients. Lymph nodes were evaluated in 196 cases with metastatic carcinoma in 29 cases (all with concurrent diagnoses of carcinoma). Most patients were alive at follow-up, 100 were lost to follow-up, and three died from other causes. Literature review revealed 2870 NIFTP cases with similar patient demographics and pathologic findings. We confirm that NIFTP is a low-risk neoplasm with indolent clinical behavior, which can be managed conservatively.

Preoperative evaluation of thyroid nodules - Diagnosis and management strategies

Thyroid cancer is the most common endocrine malignancy, with increasing incidence over the past few decades. Fine needle aspiration (FNA) biopsy is the gold standard for preoperative diagnosis of thyroid malignancies. Nevertheless, this method renders indeterminate results in up to 30% of the cases. Therefore, these patients are often referred to unnecessary surgery to establish the diagnosis. To improve the accuracy of preoperative diagnosis, several other ways, such as ultrasonography, elastography, immunohistochemical analysis, genetic testing, and core needle biopsy, have been developed and can be used either in association with or as an alternative to FNA. This review aims to evaluate all these diagnostic tools to determine the most appropriate way of managing thyroid nodules and subsequently improve the selection of cases referred to surgery.

Non-Invasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features Is Not a Cytological Diagnosis, but It Influences Cytological Diagnosis Outcomes: A Systematic Review and Meta-Analysis

BACKGROUND

A low-risk thyroid tumour, non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was introduced in 2016. NIFTP criteria require a thorough histological examination to rule out capsular and lymphovascular invasion, which denies the possibility of preoperative cytological diagnosis. Nevertheless, since the adoption of the new entity, the cytology of NIFTP has been a subject of interest.

OBJECTIVES

The present systematic review and meta-analysis investigate the cytological diagnosis of NIFTP.

METHOD

An online PubMed literature search was conducted between March 1, 2020, and June 30, 2020, for all original articles considering the cytology of histologically proven NIFTP. The studies including data on fine needle aspiration specimens classified by The Bethesda System for Reporting Thyroid Cytology (TBSRTC) categories, risk of malignancy (ROMs) in the TBSRTC categories, and cytomorphological features of NIFTP were included in the meta-analysis. Non-English studies and case reports were excluded. The data were tabulated and statistical analysis was performed with Open Meta-Analyst program.

RESULTS

Fifty-eight studies with a total of 2,553 NIFTP cases were included in the study. The pooled prevalence of NIFTP cases was calculated among 25,892 surgically resected cases from 20 studies and the results show that NIFTP consisted 4.4% (95% confidence interval [CI]: 3.5-5.4%) of all cases. Most of the NIFTP cases (79.0%) belonged to the intermediate categories of TBSRTC. The pooled distribution of NIFTP cases in each TBSRTC category was 1.3% (95% CI: 0.8-1.7%) in non-diagnostic (ND), 8.9% (95% CI: 6.9-10.8%) in benign, 29.2% (95% CI: 25.0-33.4%) in atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS), 24.2% (95% CI: 19.6-28.9%) in follicular neoplasm (FN), 19.5% (95% CI: 16.1-22.9%) in suspicious for malignancy (SM), and 6.9% (95% CI: 5.2-8.7%) in malignant. Compared to pre-NIFTP era, the pooled risk differences of ROM were reduced by 2.4% in ND, 2.7% in benign, 8.2% in AUS/FLUS, 8.2% in FN, 7.3% in SM, and 1.1% in the malignant category. The cytomorphological features of NIFTP were similar to follicular variant of papillary thyroid carcinoma (FVPTC) but lesser to papillary thyroid carcinoma (PTC).

CONCLUSIONS

Based on our results, NIFTP remains a histological diagnosis. Although cytomorphological features cannot be used in differentiating NIFTP from FVPTC, they may guide in separating NIFTP from PTC. Features such as papillae, microfollicles, giant cells, psammoma bodies, and the amount of papillary-like nuclear features should be taken into account when suspicious of NIFTP. NIFTP should not have papillae or psammoma bodies, and giant cells were rarely observed.

MiR-153 Enriched in Bone Marrow Mesenchymal Stem Cell-Derived Exosomes Promotes Chemotherapy Sensitivity of Papillary Thyroid Carcinoma

Our study assesses the effect of bone marrow mesenchymal stem cells (BMSCs) exosomes miR-153 on papillary thyroid carcinoma (PTC). Adipogenesis and osteogenic induction of MSCs was performed and labeled with Cy5 labeled miR inhibitor. Cells were transfected followed by analysis of miR-153 level by real-time PCR, P-gp level by immunoblotting, and cell viability. MSCs are non-hematopoietic bone marrow-derived cells and symmetrical fibroblasts have the same characteristics as MSCs. MSCs have the potential for adipogenesis and osteogenic differentiation; miR-Cy5 can only enter PTC cells through vesicle transfer. TMZ treatment upregulated miR-153 in exosomes; MSC-derived exosomes can be directly transferred to PTC cells. miR-153-inhibitor-Cy5 can effectively inhibit miR-153 transcription and expression of resistance-related proteins. miR-153-inhibitor can promote TMZ’s effect and lead to cell death as demonstrated by increased level of active caspase-3. Inhibiting the endogenous transcription of miR-153 by miR-153 inhibitor can significantly down-regulate cell resistance protein, thereby promoting cell apoptosis under the action of TMZ.

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: From Echography to Genetic Profile

In thyroid pathology, the great variety of types and the wide range of aggressiveness of thyroid cancers complicate both diagnosis and management. In 2016, a subset of noninvasive encapsulated follicular variant of papillary thyroid carcinoma was reclassified as noninvasive follicular thyroid tumor with papillary-like nuclear features (NIFTP) to reduce overtreatment of this low-risk tumor that follows a benign course after surgery. Starting from a paradigmatic clinical case, in this short review, we will summarize the ultrasonography, cytological, histological and molecular features of this new entity. In the preoperative settings, the recognition of some peculiar elements may only suggest the possibility of a NIFTP, thus favoring a less aggressive surgical approach. However, the diagnosis of NIFTP can only be made after complete resection of the lesion by detecting well-defined inclusion and exclusion histopathological criteria. Since NIFTP is not 'malignant,' surgery may be considered curative with no further treatment or surveillance needed. NIFTP-related issues, including nodule size, multifocality, oncocytic changes, heterogeneous incidence across different geographical areas and its occurrence in the pediatric age, will be discussed.