Histologic follow-up of nondiagnostic thyroid fine needle aspirations: Implications for adequacy criteria

Fate of nondiagnostic thyroid fine needle aspirations

BACKGROUND

Thyroid nodules may be detected during the workup of thyroid hormone abnormalities and as incidental findings during unrelated imaging studies. The diagnosis of a thyroid nodule is mainly established by performing fine needle aspiration (FNA) under ultrasound guidance. Thyroid nodules are classified as nondiagnostic, defined in the Bethesda System for Reporting Thyroid Cytopathology as samples with excess blood, cyst fluid only, and lack of thyroid follicular cells. The current study evaluates a series of nondiagnostic FNAs to assess whether repeat sampling improves yield and what patient management, and outcomes are after a nondiagnostic FNA.

METHODS

Thyroid FNAs from 2016 to 2023 were retrieved from our institution archives. All cases were performed under ultrasound guidance and with rapid on-site evaluation. Cases were assigned the Bethesda System Category. Nondiagnostic FNAs were further reviewed for repeat FNA procedures, potential molecular testing, or diagnostic resections.

RESULTS

In total 3104 thyroid FNAs were reviewed, with 153 (4.9%) being nondiagnostic. Of the 154 FNAs, there were 129 patients with an average age of 60 and a male-to-female ratio of 1:3.2. Of the 130 patients, there were 50 patients who underwent 55 repeat FNAs. Thirty-seven (67%) of the repeats were benign, 13 (24%) were nondiagnostic again, and 5 (9%) were atypia of undetermined significance (AUS). Molecular testing was performed on repeat FNAs diagnosed AUS. Four cases showed no mutations and had a high likelihood of being benign. One case did have an NRAS Q61R mutation, and resection revealed a noninvasive follicular thyroid neoplasm with papillary-like nuclear features. Seventeen (13% of all cases) with nondiagnostic FNA were resected. Twelve (71%) thyroidectomies showed benign adenomatous nodules. The remainder showed incidental papillary thyroid microcarcinoma (0.1 cm), an infarcted follicular adenoma, a noninvasive follicular thyroid neoplasm with papillary-like nuclear features, and metastatic renal cell carcinoma (2×).

CONCLUSION

Thyroid nodules with nondiagnostic cytology are reassuring of being highly likely a benign nodule. Only 5 of the 55 (9%) repeat FNAs yielded abnormalities, with only one of those being truly a follicular neoplasm (confirmed by molecular testing and resection). No primary thyroid malignancies have been identified in follow-up (repeat FNA or surgery). Clinical and ultrasound follow-up may be more appropriate management for nondiagnostic thyroid FNAs.

Insufficient endobronchial ultrasound-guided transbronchial needle aspiration specimens. When and why? The analysis of criteria and reasons behind the insufficient specimens

BACKGROUND

The classification terminology systems for pulmonary cytology specimens have recently emerged. Inadequate samples, classified as "nondiagnostic," raise challenges in determining the threshold of cell numbers and the risk of malignancy (ROM).

METHODS

The study retrospectively reviewed 248 endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) samples: 46 insufficient samples, 60 low cellularity samples, and 142 adequate samples. Characteristics as cellularity, number of benign and malignant cells, and background features were assessed. Receiver operating characteristic curve analysis was performed to establish cell sufficiency thresholds for the diagnosis.

RESULTS

Out of the 248 samples analyzed, 108 were classified as benign, 94 as malignant, and 46 as insufficient. The study found that the cellularity thresholds for diagnosis in cell blocks and cytological samples were ≥50 cells and ≥100 cells, respectively. The thresholds for tumor cell counts were ≥1 - 10 cells for both types of cells, respectively. Considerably, some low cellularity samples were initially classified as insufficient despite meeting the diagnostic thresholds upon revision. The ROM varied across sample categories, with insufficient samples having a ROM of 10.9%, benign samples 15.7%, suspicious samples 92.0%, and malignant samples 100%.

CONCLUSION

Insufficient EBUS-TBNA samples raise challenges in diagnosis and management. This study identified the root cause of insufficient samples, including factors related to humans, diagnostic methods, sampling, and laboratory processing. By understanding the root causes, diagnostic recommendations can be developed to improve the diagnostic process. The findings emphasize the importance of standardized classification and terminology systems for clear communication among healthcare professionals and institutions, ultimately improving patient care and enabling quality assurance measures.

The 2023 Bethesda System for Reporting Thyroid Cytopathology

Since the publication of the first edition in 2010, The Bethesda System for Reporting Thyroid Cytopathology has allowed cytopathologists to use a standardized, category-based reporting system for thyroid fine needle aspirations. The third edition builds on the success of the 2 earlier editions and offers several key updates. The most important is the assignment of a single name for each of the 6 diagnostic categories: (i) nondiagnostic; (ii) benign; (iii) atypia of undetermined significance; (iv) follicular neoplasm; (v) suspicious for malignancy; and (vi) malignant. Each of the categories has an implied risk of malignancy (ROM), which has been updated and refined based on data reported after the second edition. The third edition offers an average ROM for each category, in addition to the expected range of cancer risk. The atypia of undetermined significance subcategorization is simplified into 2 subgroups based on the implied ROM and molecular profiling. A discussion of pediatric thyroid disease has been added, and pediatric ROMs and management algorithms are discussed in the relevant sections. Nomenclature has been updated to align with the 2022 World Health Organization Classification of Thyroid Neoplasms. Two new chapters have been added: one that addresses the significant and expanded use of molecular and ancillary testing in thyroid cytopathology, and another that summarizes clinical perspectives and imaging findings in thyroid disease.

The 2023 Bethesda System for reporting thyroid cytopathology

Since the publication of the first edition in 2010, The Bethesda System for Reporting Thyroid Cytopathology has allowed cytopathologists to use a standardized, category-based reporting system for thyroid fine needle aspirations. The third edition builds on the success of the 2 earlier editions and offers several key updates. The most important is the assignment of a single name for each of the 6 diagnostic categories: (i) nondiagnostic; (ii) benign; (iii) atypia of undetermined significance; (iv) follicular neoplasm; (v) suspicious for malignancy; and (vi) malignant. Each of the categories has an implied risk of malignancy (ROM), which has been updated and refined based on data reported after the second edition. The third edition offers an average ROM for each category, in addition to the expected range of cancer risk. The atypia of undetermined significance subcategorization is simplified into 2 subgroups based on the implied ROM and molecular profiling. A discussion of pediatric thyroid disease has been added, and pediatric ROMs and management algorithms are discussed in the relevant sections. Nomenclature has been updated to align with the 2022 World Health Organization Classification of Thyroid Neoplasms. Two new chapters have been added: one that addresses the significant and expanded use of molecular and ancillary testing in thyroid cytopathology, and another that summarizes clinical perspectives and imaging findings in thyroid disease.

Not All Bethesda 1 Thyroid Nodules Were Created Equal: Different B1 Subgroups

OBJECTIVE

The Bethesda System for Reporting Thyroid Cytopathology is a uniform method used worldwide to report thyroid fine-needle aspiration (FNA) outcomes. This study focuses on the Nondiagnostic/Unsatisfactory category, designated as Bethesda1 (B1). The documented risk of malignancy for B1 nodules can vary significantly, implying this category is not homogenous and might be composed of different subtypes. Our hypothesis was that B1 subgroups (blood only, insufficient thyrocytes, cyst content) will vary in their malignancy rate.

METHODS

The study design was observational and retrospective. The study population included 154 patients in the Galilee Medical Center who underwent FNA examination of the thyroid gland from 2013-2018 and had a B1 result. We looked at the final diagnosis of malignant or benign for patients who underwent surgery and calculated the malignancy rate for each subgroup.

RESULTS

Malignancy rates were higher in the Blood subgroup than in the other subgroups, and higher in the Thyrocytes subgroup than in the Cyst subgroup (P < .05). All malignancies were papillary thyroid carcinomas. There was no significant difference in the malignancy rate when we further divided the B1 samples into 2 groups based on the presence of epithelial cells. Many repeat FNA tests resulted in a different B1 subgroup.

CONCLUSION

The different malignancy rates suggest that individual management approaches should be considered for each B1 subgroup.

Impact of cytological pitfalls in the Bethesda System of Reporting Thyroid Cytopathology, on surgical decision-making of patients with thyroid nodules: Can these pitfalls be avoided?

INTRODUCTION

The purpose was to assess diagnostic accuracy of the Bethesda System of Reporting Thyroid Cytopathology, reasons for disagreement and cytological pitfalls with impact on surgical decisions in patients with thyroid nodules.

METHODS

Cases of thyroid cytology with histological follow up were included followed by cytological-histological correlation and were reviewed to look for reasons for discrepancies. The impact of disagreements and partial agreements on surgical decision was evaluated. Overall and complete diagnostic accuracy were calculated along with sensitivity, specificity, and positive and negative predictive values for malignant and neoplastic lesions.

RESULTS

Of 446 cases included in the study, there was complete agreement in 358 cases, partial agreement in 22 cases and disagreement in 66 patients. Overall diagnostic accuracy was 98.5% with sensitivity, specificity, positive predictive value and negative predictive value of 80%, 99.6%, 100%, 72.7% and 94.3% respectively for malignant lesions. Overall diagnostic accuracy was highest for the malignant category. Follicular patterned lesions, Hürthle cell-rich smears and overlapping cytological features between benign and malignant follicular neoplasm were the main reason of discrepancy. The discrepancy in cytological diagnosis altered the decision of type of surgery performed in 13.6% of the patients.

CONCLUSION

Fine needle aspiration cytology remains a powerful screening tool to aid decision-making in the majority of the patients. Histological-cytological discrepancy can adversely impact the management of patients. Factors causing an adverse impact on surgical management were rare and potential avoidable reasons for them were identified. Cytological pitfalls may be avoided through screening for minor components, clinico-radiological correlation and experience.

Cytologic diagnosis of medullary thyroid carcinoma in the Asia-Pacific region

BACKGROUND

The accurate preoperative identification of medullary thyroid carcinoma (MTC) is challenging due to the rarity of tumor and variable cytologic appearance. The Asian experience with diagnosing MTC by fine-needle aspiration (FNA) was scarcely reported.

METHODS

Cases of MTC with available FNA slides were enrolled from 13 hospitals representing 8 Asia-Pacific countries. Clinicopathological information, including sample preparation technique, staining method, original cytologic diagnosis and review diagnosis were collected.

RESULTS

Of a total of 145 MTC cases retrospectively recruited, 99 (68.3%) were initially interpreted as MTC/suspicious for MTC (S-MTC). The distribution of original FNA diagnostic categories was not associated with the staining method or sample preparation technique. The staining methods used were Papanicolaou, hematoxylin-eosin and Romanowsky stains. Liquid-based cytology (LBC) was used only in three countries. After reviewing all cases, the diagnostic rate of MTC/S-MTC increased to 91.7% (133/145). Cases with initially unrecognized MTC had either marked pleomorphism or cytology mimicking papillary carcinoma or follicular neoplasm. Although LBC provided certain benefits, there was no significant difference in diagnostic accuracy between conventional smear and LBC. Immunocytochemistry was available in 38 cases (26.2%), all of which were correctly recognized as MTC.

CONCLUSION

Our report summarizes how MTC is handled in contemporary Asian thyroid FNA practice. Although the detection rate of MTC by cytology alone is less satisfactory, integration with ancillary tests could achieve an excellent performance. The recognition of constitutive cytomorphologic features is needed for each cytopreparatory method, which may result in a lower threshold to initiate further workup for MTC.

Preanalytic variables in quality and quantity of nucleic acids extracted from FNA specimens of thyroid gland nodules collected in CytoLyt: Cellularity and storage time

BACKGROUND

Morphologic and genetic analysis of thyroid nodules may be performed from a single vial. Preanalytic variables that affect nucleic acid extracted from a single vial are evaluated.

METHODS

Thyroid fine-needle aspiration (FNA) specimens collected in CytoLyt were evaluated. A ThinPrep slide was prepared. Extracted nucleic acids were analyzed using Oncomine Comprehensive Panel, version 2, after Ion AmpliSeq library preparation. A pathologist and a cytotechnologist enumerated specimen cellularity.

RESULTS

Fifty-six samples were collected from 55 nodules in 53 patients. Bethesda category correlated with cellularity (P = .01), and storage time (median, 43 days; range, 7-77 days) was longer for specimens in categories II and III than for those in categories IV and VI (P = .01). The mean specimen DNA concentration was 4.5 ng/µL (range, 0-23.8 ng/µL), and 25 (45%) had concentrations >3.3 ng/µL. The mean specimen RNA concentration was 4.8 ng/µL (range, 0-42.4 ng/µL), and 31 (55%) had concentrations >1.4 ng/µL. Nucleic acid quantity increased with epithelial cellularity. Storage time weakly correlated with the quantity of extracted DNA, independent of cellularity, but not extracted RNA. Greater proportions of cell-free DNA and lesser proportions of long, intact RNA fragments were extracted from a subset of samples with longer storage time. Among 15 single nucleotide variants, the median mutant allelic fraction was 15.1%. One false-negative result was identified. Five specimens subsequently determined to harbor a genetic alteration failed quality metrics.

CONCLUSIONS

Cellularity and storage time affect the quantity and quality of nucleic acid extracted from thyroid FNA specimens collected in CytoLyt. Further investigation will serve to quantify the magnitude of such effects and to elucidate other contributing factors.

Thyroid FNA: Is cytopathologist review of ultrasound features useful?

Cytopathologist review of thyroid ultrasound (US) has been proposed to be useful in diagnosis and patient triage. This review explores the implications for practicing cytopathologists of integrating US review into the thyroid fine-needle aspiration diagnosis. At present, there is no agreed-upon system for combining cytologic and US features and communicating those results as a single report. If cytologists are performing tasks that require expertise in US interpretation, then they should know and be fully conversant with US interpretation. Whether cytologists performing aspirations require expertise in US interpretation is not clear. Regardless, cytologists should avoid using US results to alter their cytologic interpretations unless they clearly communicate that this is what they are doing. An evidence-based integrated reporting system that would allow cytologists to clearly explain to other physicians exactly how they reached their interpretation might provide value beyond current standard practice.

Modified Bethesda system informing cytopathologic adequacy improves malignancy risk stratification in nodules considered benign or atypia(follicular lesion) of undetermined significance

We modified the nondiagnostic/unsatisfactory category of the Bethesda system for reporting thyroid cytopathology to inform cytopathologic adequacy to better stratify the malignancy risk. Malignancy rates from 1,450 cytopathologic specimens not satisfying adequacy criteria from April 2011 to March 2016 were calculated based on sub-classification of the nondiagnostic/unsatisfactory category and sonographic patterns using matched surgical pathology. Rates were compared with those of 1,446 corresponding adequate specimens from July to December 2013. Upon resection, 63.2% of nondiagnostic, 36.7% of unsatisfactory + benign, 72.5% of unsatisfactory + atypia (follicular lesion) of undetermined significance, 98.1% of unsatisfactory + suspicious for malignancy, and 100.0% of unsatisfactory + malignant cases were confirmed to be malignant on surgical pathology. In nodules with inadequate specimens, those with high suspicion sonographic patterns had a malignancy rate (93.2%) higher than the others (45.5%) (p < 0.001). Nodules with unsatisfactory + benign specimens had a higher malignancy rate (36.7%) than satisfactory benign specimens (14.3%) (p = 0.020). For atypia (follicular lesion) of undetermined significance, the malignancy rate of inadequate specimens (72.5%) was higher than that of adequate specimens (51.3%) (p = 0.027). Sparse cellular samples with a few groups of benign follicular cells should not represent a benign lesion. There might be value in qualifying atypia (follicular lesion) of undetermined significance cases less than optimal.

The 2017 Bethesda System for Reporting Thyroid Cytopathology

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) established a standardized, category-based reporting system for thyroid fine-needle aspiration (FNA) specimens. The 2017 revision reaffirms that every thyroid FNA report should begin with one of six diagnostic categories, the names of which remain unchanged since they were first introduced: (i) nondiagnostic or unsatisfactory; (ii) benign; (iii) atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS); (iv) follicular neoplasm or suspicious for a follicular neoplasm; (v) suspicious for malignancy; and (vi) malignant. There is a choice of two different names for some of the categories. A laboratory should choose the one it prefers and use it exclusively for that category. Synonymous terms (e.g., AUS and FLUS) should not be used to denote two distinct interpretations. Each category has an implied cancer risk that ranges from 0% to 3% for the "benign" category to virtually 100% for the "malignant" category, and, in the 2017 revision, the malignancy risks have been updated based on new (post 2010) data. As a function of their risk associations, each category is linked to updated, evidence-based clinical management recommendations. The recent reclassification of some thyroid neoplasms as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) has implications for the risk of malignancy, and this is accounted for with regard to diagnostic criteria and optional notes. Such notes can be useful in helping guide surgical management.

The 2017 Bethesda System for Reporting Thyroid Cytopathology

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) established a standardized, category-based reporting system for thyroid fine-needle aspiration (FNA) specimens. The 2017 revision reaffirms that every thyroid FNA report should begin with 1 of 6 diagnostic categories, the names of which remain unchanged since they were first introduced: (1) Nondiagnostic or Unsatisfactory; (2) Benign; (3) Atypia of Undetermined Significance (AUS) or Follicular Lesion of Undetermined Significance (FLUS); (4) Follicular Neoplasm or Suspicious for a Follicular Neoplasm; (5) Suspicious for Malignancy; and (6) Malignant. There is a choice of two different names for some of the categories: a laboratory should choose the one it prefers and use it exclusively for that category; synonymous terms (eg, AUS and FLUS) should not be used to denote 2 distinct interpretations. Each category has an implied cancer risk that ranges from 0% to 3% for the "Benign" category to virtually 100% for the "Malignant" category, and, in the 2017 revision, the malignancy risks have been updated based on new (post 2010) data. As a function of their risk associations, each category is linked to updated, evidence-based clinical management recommendations. The recent reclassification of some thyroid neoplasms as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) has implications for the risk of malignancy, and this is accounted for with regard to diagnostic criteria and optional notes. Such notes can be useful in helping guide surgical management.

Impact of Noninvasive Follicular Thyroid Neoplasm With Papillary-Like Features on Adequacy Criteria and Risk of Malignancy of Thyroid Fine-Needle Aspiration

OBJECTIVES

The impact of noninvasive follicular thyroid neoplasm with papillary-like features (NIFTP) on nondiagnostic and benign diagnoses is not well characterized.

METHODS

The results of all thyroid fine-needle aspirates (FNAs) performed from 1997 to June 2016 with corresponding resections were reviewed.

RESULTS

From 12,764 aspirates, there were 8,106 (64%) benign diagnoses with 412 (5%) resections and 1,888 (14.8%) nondiagnostic diagnoses with 329 (17%) resections. Before the use of NIFTP, there were 18 (4.3%) malignancies in the benign aspirates and 39 (11.9%) malignancies in the nondiagnostic aspirates. There were 12 NIFTP cases on review. After reclassification using NIFTP, there were 10 of 412 (2.4%) malignancies in the benign aspirates. When cases with 10 to 60 benign follicle cells without atypia or Hürthle cell change were reclassified as benign rather than nondiagnostic, the malignancy rate for a benign aspirate decreased (12/506, 2.3%; P = 1.0) when NIFTP cases were recognized.

CONCLUSIONS

With NIFTP, reducing the threshold for adequacy from 60 to 10 cells led to nonsignificant decrease in the risk of malignancy of a benign diagnosis (2.4% to 2.3%). Thyroid fine-needle aspirates with 10 to 60 benign cells without atypia or Hürthle cell change should be diagnosed as benign.

Thyroid nodules with macrocalcification: sonographic findings predictive of malignancy

PURPOSE

To analyze which sonographic features of thyroid nodules with macrocalcifications were predictable of thyroid malignancy.

MATERIALS AND METHODS

We reviewed sonographic findings of 854 macrocalcified thyroid nodules in patients who underwent fine needle aspiration biopsy between December 2009 and January 2011. There were 171 non-diagnostic aspirations, 34 nodules with category 3, 4, 5 based on Bethesda system, which were not confirmed by surgery, and these nodules were excluded from the analysis. Sonographic characteristics of the macrocalcifications including its thickness, interruption, and existence of soft tissue rim outside the macrocalcification were analyzed. Other sonographic characteristics of nodules such as shape, margin, composition, echo pattern, vascularity, and underlying parenchymal echogenicity were also evaluated. The correlation of sonographic features with cytopathologic results and the diagnostic performance of sonographic features for the prediction of malignancy were analyzed.

RESULTS

Among 649 nodules, 179 (27.6%) nodules were malignant and 470 (72.4%) nodules were benign. Among the features of the macrocalcification, interruption, irregular thickness, or the presence of soft tissue outside calcification rim were associated with malignancy (p<0.001). A high sensitivity and negative predictive values for the prediction of malignancy was found in sonographic characteristics of irregular thickness (92.2% and 91.0%, respectively) and the presence of soft tissue (88.5% and 88.8%, respectively).

CONCLUSION

Sonographic characteristics of macrocalcification such as interruption, irregular thickness and the presence of soft tissue rim were associated with malignancy in thyroid nodules with macrocalcifications.

Significance of repeatedly nondiagnostic thyroid fine-needle aspirations

Nondiagnostic thyroid fine-needle aspirations are associated with a risk of malignancy that can be reduced with repeated aspiration. However, the significance of repeated nondiagnostic aspirates is less well studied. This study assessed the risk of malignancy for repeated nondiagnostic aspirates from a large series of cases using the results of histologic follow-up. From a series of 7,089 aspirates, there were 1,671 nondiagnostic aspirates (23.6%), and 235 of these (14.1%) had histologic follow-up. The risk of malignancy for a single nondiagnostic aspirate was 20.0% (47/235). A total of 51 cases had repeated aspiration. The risk of malignancy for cases with a second nondiagnostic aspirate was 0% (0/23), which was significantly less than for patients with a single nondiagnostic aspirate (20.0%; P = .03). Patients with 2 sequential nondiagnostic thyroid aspirates have a very low risk of malignancy. Cytologists should strive to better convey this risk in their reports.