Hürthle cell carcinoma is a better gold standard than Hürthle cell neoplasm for fine-needle aspiration of the thyroid: defining more consistent and specific cytologic criteria

A case series of thyroid fine needle aspiration biopsies diagnosed as follicular neoplasm with oncocytic features

Oncocytic lesions of the thyroid are a heterogeneous group encompassing nonneoplastic and neoplastic entities ranging from benign to malignant and have traditionally been classified as separate entities in thyroid pathology. To illustrate the diversity of these thyroid lesions, we describe three cases of fine needle aspiration biopsies (FNAB) diagnosed as Bethesda Category IV: Follicular neoplasm, oncocytic type, under the 2017 Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), with ThyroSeq v3 molecular testing and subsequent surgical excision.

"Copy number alteration" as the sole molecular finding of a Thyroseq test is more commonly seen in Hurthle cell neoplasms

BACKGROUND

To better understand the molecular alterations associated with Hurthle cell lesions of the thyroid, we retrospectively reviewed the association of clonal DNA copy number alterations (CNAs) with fine needle aspiration (FNA) cytomorphology and surgical follow-up.

METHODS

Hurthle cell type (HCT) and non-Hurthle cell type (NHCT) thyroid FNAs that were classified according to the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) as atypia of undetermined significance (AUS) and suspicious for a follicular neoplasm (SFN) with corresponding molecular testing performed by ThyroSeq v3 genomic classifier were compared to surgical follow-up.

RESULTS

A total of 54 thyroid FNA cases were identified, distributed among the following categories: AUS-HCT (n = 15, 27.8%), SFN-HCT (n = 11, 20.4%), AUS-NHCT (n = 19, 35.2%), and SFN-NHCT (n = 9, 16.6%). The lesions classified as AUS-HCT and SFN-HCT showed a higher prevalence of CNAs (n = 10/26; 38.5%) compared to their NHCT counterparts (n = 3/28; 10.7%) (p < .03). Of the 42 patients (77.8%) with surgical follow-up, CNAs were more often seen in benign (n = 10/26, 38.5%) than malignant conditions (n = 1/16, 6.3%) (p < .03). CNAs were encountered in more lesions with Hurthle cell features on histologic examination (n = 8/14, 57.1%) than those without (n = 3/28, 10.7%) (p < .002). The presence of CNAs alone was seen only in benign adenomas and more commonly with Hurthle cell features (n = 5/7, 71.4%).

CONCLUSION

In this study, CNAs were associated with Hurthle cell morphology on thyroid FNA and benign adenomas upon surgical follow-up. Therefore, if the only finding of a positive ThyroSeq v3 GC result is a CNA, conservative management can be considered if clinically indicated.

Hürthle cell-predominant thyroid fine needle aspiration cytology: A four risk-factor model highly accurate in excluding malignancy and predicting neoplasm

Background

Interpretation of Hürthle cell‐predominant cytologies (HCP) is very challenging as a majority is diagnosed as indeterminate. Prior studies have reported various cytologic features to help distinguish non‐neoplastic (NN) from neoplastic and malignant lesions but had contradicting results. Our aim was to identify risk factors predictive of neoplasm and/or malignancy by correlating cytologic features with clinical and ultrasound findings.

Methods

Sixty‐nine HCP cases with surgical follow‐up were identified, including 35 NN, 20 adenomas, and 14 carcinomas. Ultrasound data were recorded utilizing Thyroid Imaging Reporting and Data System (TI‐RADS) and American Thyroid Association (ATA) scoring systems. Sixteen cytologic criteria were evaluated and semi‐quantitatively scored. Data were assessed by univariable, multivariable and stepwise logistic regression analysis; and statistical significance achieved at P‐value <0.05.

Results

On univariable analysis, significant predictors of neoplasm were high cellularity, isolated single cells, absent colloid, non‐uniform HC population (anisonucleosis), larger nodule size, and higher ATA score. Large‐cell dysplasia and transgressing blood vessels were not found to be significant factors. Multivariable analysis identified a combination of four risk factors (high cellularity, anisonucleosis, absent colloid, and size ≥2.9 cm) that was associated with neoplasm in 10/11 patients. None of 15 patients with zero or 1 out of 4 risk factors had malignancy or neoplasm on follow‐up. This model also significantly outperformed ATA and TI‐RADS scoring systems.

Conclusion

In the absence of four or three risk factors, the model excluded malignancy and neoplasm in all patients. The presence of all four factors predicted neoplasm and malignancy in 91% and 46% of cases, respectively.

Copy number variations identified in thyroid FNA specimens are associated with Hürthle cell cytomorphology

BACKGROUND

The fine-needle aspiration (FNA) diagnosis of thyroid Hürthle cell neoplasms (HCNs) remains challenging. This study explored a possible association of copy number variations (CNVs) with Hürthle cell lesions of the thyroid.

METHODS

Thyroid FNA cases that were diagnosed as follicular lesion of undetermined significance (FLUS) or follicular neoplasm (FN)/HCN for which the ThyroSeq version 3 genomic classifier test was performed were retrieved.

RESULTS

A total of 324 thyroid FNA cases (228 FLUS cases, 46 HCN cases, and 50 FN cases) were included in the study. FLUS cases were further classified as Hürthle cell type (follicular lesion of undetermined significance-Hürthle cell type [FLUS-HCT]; 20 cases) or non-Hürthle cell type (follicular lesion of undetermined significance-non-Hürthle cell type [FLUS-NHCT]; 208 cases). HCN and FLUS-HCT cases showed a higher prevalence of CNVs (23 of 66 [35%]) in comparison with those classified as FN or FLUS-NHCT (14 of 258 [5%]; P < .001). A total of 105 patients had histopathologic follow-up. Cases with CNVs were more likely to be neoplastic (18 of 26 [69%]) and associated with Hürthle cell changes (14 of 26 [54%]) in comparison with cases without any molecular alterations (neoplastic, 8 of 24 [33%]; Hürthle cell changes, 2 of 24 [8%]; P < .05). In HCN/FLUS-HCT cases with CNVs (n = 14), Hürthle cell changes (13 of 14 [93%]) and neoplasms (9 of 14 [64%]) were more likely to be seen on surgical follow-up in comparison with the 17 cases without CNVs (Hürthle cell changes, 6 of 17 [35%]; neoplastic, 3 of 17 [18%]; P < .05).

CONCLUSIONS

CNVs identified in thyroid FNA cases are associated with Hürthle cell morphology and are suggestive of a neoplasm with Hürthle cell features in thyroid FNAs classified as FLUS-HCT/HCN. This finding may be helpful in triaging patients who would benefit from surgical management.

Challenges in Cytology Specimens With Hürthle Cells

In fine-needle aspirations (FNA) of thyroid, Hürthle cells can be found in a broad spectrum of lesions, ranging from non-neoplastic conditions to aggressive malignant tumors. Recognize them morphologically, frequently represents a challenging for an adequately diagnosis and are associated with a significant interobserver variability. Although the limitations of the morphologic diagnosis still exist, the interpretation of the context where the cells appear and the recent advances in the molecular knowledge of Hürthle cells tumors are contributing for a more precise diagnosis. This review aims to describe the cytology aspects of all Hürthle cells neoplastic and non-neoplastic thyroid lesions, focusing on the differential diagnosis and reporting according to The Bethesda System for Reporting Thyroid Cytology (TBSRTC). New entities according to the latest World Health Organization (WHO) classification are included, as well as an update of the current molecular data.

Thyroid Hürthle Cell Carcinoma: Clinical, Pathological, and Molecular Features

Simple Summary

Hürthle cell carcinoma (HCC) represents 3–4% of thyroid carcinoma cases. It is characterized by its large, granular and eosinophilic cytoplasm, due to an excessive number of mitochondria. Hürthle cells can be identified only after fine needle aspiration cytology biopsy or by histological diagnosis after the surgical operation. Published studies on HCC indicate its putative high aggressiveness. In this article, current knowledge of HCC focusing on clinical features, cytopathological features, genetic changes, as well as pitfalls in diagnosis are reviewed in order to improve clinical management.

Abstract

Hürthle cell carcinoma (HCC) represents 3–4% of thyroid carcinoma cases. It is considered to be more aggressive than non-oncocytic thyroid carcinomas. However, due to its rarity, the pathological characteristics and biological behavior of HCC remain to be elucidated. The Hürthle cell is characterized cytologically as a large cell with abundant eosinophilic, granular cytoplasm, and a large hyperchromatic nucleus with a prominent nucleolus. Cytoplasmic granularity is due to the presence of numerous mitochondria. These mitochondria display packed stacking cristae and are arranged in the center. HCC is more often observed in females in their 50–60s. Preoperative diagnosis is challenging, but indicators of malignancy are male, older age, tumor size > 4 cm, a solid nodule with an irregular border, or the presence of psammoma calcifications according to ultrasound. Thyroid lobectomy alone is sufficient treatment for small, unifocal, intrathyroidal carcinomas, or clinically detectable cervical nodal metastases, but total thyroidectomy is recommended for tumors larger than 4 cm. The effectiveness of radioactive iodine is still debated. Molecular changes involve cellular signaling pathways and mitochondria-related DNA. Current knowledge of Hürthle cell carcinoma, including clinical, pathological, and molecular features, with the aim of improving clinical management, is reviewed.

Preoperative diagnostic categories of fine needle aspiration cytology for histologically proven thyroid follicular adenoma and carcinoma, and Hurthle cell adenoma and carcinoma: Analysis of cause of under- or misdiagnoses

Cytologic diagnosis of thyroid follicular adenoma and carcinoma, and Hurthle cell adenoma and carcinoma (FACHAC) is challenging due to cytomorphologic features that overlap with other follicular-patterned lesions. This study was designed to analyze diagnostic categories (DCs) of preoperative fine needle aspiration cytology (FNAC) of histologically proven thyroid FACHACs to evaluate under- or misdiagnoses in FNAC and elucidate potential causes for such phenomena. A total of 104 thyroid nodules with preoperative FNAC which were diagnosed as FACHAC in resection specimens were included in this study. Of these, 66 cases had also undergone thyroid core needle biopsy (CNB); FNAC and CNB DCs were compared in these cases. Various cytologic and histologic parameters were compared between the nodules with different FNAC DCs. After a review of FNAC slides, DCs were re-assigned in 20 (19.2%) out of the 104 cases. Of the 66 cases with CNB diagnoses which were mostly classified as lower DCs in FNAC, 31 (47.0%) were diagnosed as suspicious for a follicular neoplasm in CNB. Cases which were underdiagnosed in FNACs were associated with lower cellularity, predominant macrofollicular pattern, absence of microfollicles arranged in trabecular pattern, and absence of transgressing vessels in cytology smears. High cellularity, microfollicles arranged in trabecular pattern, nucleolar prominence, and large cell dysplasia were more frequently found in malignancy than in benign neoplasm. In conclusion, thyroid FACHACs seem to be under- and misdiagnosed in preoperative FNAC. Innate characteristics of the nodules were associated with under-diagnosis as well as the quality of the FNAC specimens. Certain cytomorphologic features can be helpful in differentiating malignancy among FACHACs.

Hürthle cell lesions of the thyroid: Progress made and challenges remaining

Hürthle cell-predominant thyroid fine needle aspirations (FNA) are encountered frequently in routine practice, yet they are often challenging to diagnose accurately and are associated with significant interobserver variability. This is largely due to the ubiquity of Hürthle cells in thyroid pathology, ranging from nonneoplastic conditions to aggressive malignancies. Although limitations in cytomorphologic diagnoses likely will remain for the foreseeable future, our knowledge of the molecular pathogenesis of Hürthle cell neoplasia and application of molecular testing to cytologic material have increased dramatically within the past decade. This review provides context behind the challenges in diagnosis of Hürthle cell lesions and summarizes the more recent advances in diagnostic tools.

DNA FISH Diagnostic Assay on Cytological Samples of Thyroid Follicular Neoplasms

Simple Summary

Cytopathology cannot distinguish benign from malignant follicular lesions in 20–30% of cases. These indeterminate cases includes the so-called follicular neoplasms (FNs) according to The Bethesda System for Reporting Thyroid Cytopathology. Frozen samples from 66 classic follicular adenomas (cFAs) and carcinomas (cFTCs) studied by array-comparative genomic hybridization identified three specific alterations of cFTCs (losses of 1p36.33-35.1 and 22q13.2-13.31, and gain of whole chromosome X) confirmed by fluorescent in situ hybridization (FISH) in a second independent series of 60 touch preparations from frozen samples of cFAs and cFTCs. In a third independent set of 27 cases of already stained pre-operative fine-needle aspiration cytology samples diagnosed as FNs and histologically verified, FISH analysis using these three markers identified half of cFTCs. Specificity of our assay for identifying cFTCs is higher than 98% which might be comparable with BRAF^600E testing in cases of suspicion of classic papillary thyroid carcinomas.

Abstract

Although fine-needle aspiration cytology (FNAC) is helpful in determining whether thyroid nodules are benign or malignant, this distinction remains a cytological challenge in follicular neoplasms. Identification of genomic alterations in cytological specimens with direct and routine techniques would therefore have great clinical value. A series of 153 cases consisting of 72 and 81 histopathologically confirmed classic follicular adenomas (cFAs) and classic follicular thyroid carcinomas (cFTCs), respectively, was studied by means of different molecular techniques in three different cohorts of patients (pts). In the first cohort (training set) of 66 pts, three specific alterations characterized by array comparative genomic hybridization (aCGH) were exclusively found in half of cFTCs. These structural abnormalities corresponded to losses of 1p36.33-35.1 and 22q13.2-13.31, and gain of whole chromosome X. The second independent cohort (validation set) of 60 pts confirmed these data on touch preparations of frozen follicular neoplasms by triple DNA fluorescent in situ hybridization using selected commercially available probes. The third cohort, consisting of 27 archived cytological samples from an equal number of pts that had been obtained for preoperative FNAC and morphologically classified as and histologically verified to be follicular neoplasms, confirmed our previous findings and showed the feasibility of the DNA FISH (DNA fluorescent in situ hybridization) assay. All together, these data suggest that our triple DNA FISH diagnostic assay may detect 50% of cFTCs with a specificity higher than 98% and be useful as a low-cost adjunct to cytomorphology to help further classify follicular neoplasms on already routinely stained cytological specimens.

Malignancy risk for solitary and multiple nodules in Hürthle cell-predominant thyroid fine-needle aspirations: A multi-institutional study

BACKGROUND

Hürthle cell metaplasia is common in hyperplastic nodules, particularly within the setting of lymphocytic thyroiditis (LT). The Bethesda System for Reporting Thyroid Cytopathology indicates that it is acceptable to classify Hürthle cell-predominant fine-needle aspiration (HC FNA) specimens as atypia of undetermined significance (AUS) rather than suspicious for a Hürthle cell neoplasm (HUR) within the setting of multiple nodules or known LT. The goal of the current study was to address whether this approach is justified.

METHODS

HC FNA specimens were identified and correlated with ultrasound and surgical pathology reports if available. Multinodularity was determined based on findings on macroscopic examination if imaging results were unavailable.

RESULTS

A total of 698 HC FNA specimens were identified, including 576 resected nodules, 455 of which (79%) were benign. The overall risk of malignancy for HUR was 27%, whereas the risk of malignancy for AUS was 10%. The mean size of the benign nodules was 2.1 cm on surgical resection specimens, with multiple nodules noted in 293 cases (64%) and histologic LT noted in 116 cases (25%). The mean size of the malignant nodules was 2.8 cm, with multiple nodules and histologic LT noted in 74 cases (61%) and 22 cases (18%), respectively. The malignancy rate did not differ between solitary or multiple nodules (P = .52) or in the presence or absence of LT (P = .12). However, size did significantly differ between malignant and benign nodules (P < 0.01).

CONCLUSIONS

The malignancy rate did not differ significantly in the presence of multiple nodules or LT, although the latter demonstrated a statistical trend. A diagnosis of AUS over HUR based solely on the presence of multinodularity is not warranted.

Cytologic Diagnosis of Oncocytic Neoplasms of the Thyroid Gland: The Importance of the Clinical Scenario

It is a diagnostic challenge to differentiate benign and malignant thyroid neoplasms made up of Hürthle (or oncocytic) cells on cytologic material. They are large, polygonal cells with marked eosinophilic, granular cytoplasm reflective of overly abundant mitochondria. These cells commonly occur in nodular goiters and dominant adenomatous or hyperplastic nodules though they may also be the predominant component of neoplastic lesions. There are significant controversies concerning the optimal management of patients with oncocytic cell carcinoma. This review provides an overview of the most significant studies addressing the distinction between benign and malignant Hürthle cell lesions on cytology and histology.

Follicular thyroid cancer and Hürthle cell carcinoma: challenges in diagnosis, treatment, and clinical management

Follicular thyroid cancer is the second most common differentiated thyroid cancer histological type and has been overshadowed by its more common counterpart-papillary thyroid cancer-despite its unique biological behaviour and less favourable outcomes. In this Review, we comprehensively review the literature on follicular thyroid cancer to provide an evidence-based guide to the management of these tumours, to highlight the lack of evidence behind guideline recommendations, and to identify changes and challenges over the past decades in diagnosis, prognosis, and treatment. We highlight that correct identification of cancer in indeterminate cytological samples is challenging and ultrasonographic features can be misleading. Despite certain unique aspects of follicular thyroid cancer presentation and prognosis, no specific recommendations exist for follicular thyroid cancer and Hürthle cell carcinoma in evidence-based guidelines. Efforts should be made to stimulate additional research in this field.

Preoperative Diagnosis of Neoplastic or Malignant Hürthle Cell Lesions: A Chimera?

OBJECTIVE

We aimed to review all cytological specimens with Hürthle cells (HC) diagnosed in our institution, identify cytological features related to neoplastic (adenoma or carcinoma) and malignant histology, and discuss the role of clinicopathological findings and clinical management in these cases.

STUDY DESIGN

We included 359 thyroid fine-needle aspiration cytology cases in our study. We reviewed the clinical and cytological features of surgical cases and correlated them with histological diagnosis. We also reviewed the literature on this issue.

RESULTS

We found a significant association between neoplasia and highly cellular smears, the absence of colloid, the presence of microfollicles, large-cell dysplasia, prominent nucleoli or macronucleoli, coarse chromatin, nuclear grooves and inclusions, nuclear irregularity, and pleomorphism. The absence of colloid, high cellularity, > 25% of isolated HC, the presence of tridimensional groups, transgressing vessels, nuclear irregularity, prominent nucleoli or macronucleoli, coarse chromatin, hyperchromatism, pleomorphism, and diffuse large-cell dysplasia were features significantly associated with malignancy.

CONCLUSIONS

No cytological feature alone can predict histological outcome, but all findings related to a neoplastic or malignant histology must be assessed. Individualized management protocols should be developed in each institution.

CORRELATIONS BETWEEN THE PRESENCE OF HÜRTHLE CELLS AND CYTOMORPHOLOGICAL FEATURES OF FINE-NEEDLE ASPIRATION BIOPSY IN THYROID NODULES

Introduction

The presence of Hürthle cells (HC) in fine needle thyroid biopsy (FNAB) is a real concern for a cytologist and also for an endocrinologist. We aimed to demonstrate if the presence of HC is associated with specific cytological features in FNAB results.

Material and Methods

This retrospective study analyzed 89 patients diagnosed with thyroid nodules, with FNAB; were two groups of patients: the study group A (HC+) (22 patients) with HC and control group B (HC-) (67 patients) with no HC; for both groups we analyzed the presence of 9 cytomorphologic features: overall cellularity, background colloid, lymphocyte infiltration, chronic inflammation, large nucleoli, small nucleoli, syncytial infiltration, nuclear pleomorphism/atypia, cellular pleomorphism.

Results

We found no statistical differences between age and gender. Nodules with diameter greater than 2 cm were present, more frequently in the group without HC, 43 (64.18%). The presence of HC is correlated with cellular pleomorphism (p=0.042) and nuclear pleomorphism (p < 0.0001) with no correlation between the other investigated parameters. The presence of colloid was correlated with the absence of HC (p= 0.014). In group with HC was a positive correlation with cellular pleomorphism and fibrosis. In the presence of fibrosis, HC was correlated with nuclear pleomorphism (p=0.03). In the group with HC without fibrosis there are more characteristic the sets with positive nuclear pleomorphism, positive large nucleoli and negative small nucleoli (p= 0.002).

Conclusions

The presence of HC in FNAB results is associated with colloid in small amounts, associated with nodules smaller than 2 cm, correlated with cellular pleomorphism and nuclear pleomorphism. Fibrosis can be a protective feature against malignancy because cellular parameters were not significantly associated with HC except the cellular pleomorphism.

Thyroid FNAC containing hürthle cells and hürthle-like cells: A study of 128 cases

Aim:

It is a diagnostic challenge to differentiate benign and malignant cytology in the presence of Hürthle cells. In our previous study, it was determined that in fine needle aspirations (FNA), the malignancy outcome of the Hürthle cells containing group tend to be papillary thyroid carcinoma (PTC) in a higher percentage. The most common misinterpretation is caused by PTC cells with large cytoplasm-like Hürthle cells. The aim of this study is to predict histologic outcome of the nodules, which have Hürthle cells in FNA according to cytological, clinical features, and BRAF^V600E mutation status.

Materials and Methods:

Detailed cytological features of 128 cases were compared with histopathological diagnosis. The analysis of BRAF^V600E mutation of the PTC cases were performed by real-time polymerase chain reaction.

Results:

The neoplastic outcome was increased statistically significantly with younger age (P = 0.020), increase in cellular dyshesion (P = 0.016), presence of nuclear budding (P = 0.046), and granular chromatin (P = 0.003). Nuclear budding (P = 0.014), granular chromatin (P = 0.012), and hypoechoic nodules in ultrasonography (P = 0.011) were significant independent factors for the increase in the malignancy risk. Increased lymphocytes (P= 0.015) and colloid were related to non-neoplastic outcome. According to the surgical outcome, more than half of the malign cases were PTC (74%). BRAF^V600E mutation was detected in 27.8% of the PTC cases.

Conclusion:

PTC cases containing Hürthle cell-like cells may lead to diagnostic errors. Nuclear budding and granular chromatin of Hürthle cells are significant, remarkable findings to predict the outcome of neoplasm and malignancy.

Fine-needle aspiration cytology of thyroid nodules with Hürthle cells: cytomorphologic predictors for neoplasms, improving diagnostic accuracy and overcoming pitfalls

OBJECTIVES

Hürthle cells (HCs) are follicular-derived oncocytic cells seen in a variety of neoplastic and nonneoplastic pathologic entities of the thyroid gland. This study was to report our experience of the surgical outcome on the finding of HCs on fine-needle aspiration biopsies (FNABs) of thyroid nodules, to identify cytologic predictors of HC neoplasms and an attempt to overcome diagnostic pitfalls.

STUDY DESIGN

This was a retrospective study of all FNAB of thyroid nodules with findings of HCs with subsequent surgical resection. The FNAB slides of 70 thyroid nodules were blindly reviewed for specific cytomorphologic characteristics. The cytologic findings were correlated with the corresponding final surgical pathology diagnosis.

RESULTS

The patients ranged in age from 25 to 78 years with a male:female ratio of 1:2. There were 19 false-negative and 4 false-positive cases. Overall high cellularity, scant colloid and >90% HCs on FNAB are consistently seen in a neoplastic HC process. All cases of Hashimoto's thyroiditis were associated with prominent nucleoli and 92% of cases demonstrating transgressing vessels were neoplastic.

CONCLUSION

Diagnostic accuracy can be improved by following the current Bethesda classification system. A constellation of cytomorphologic features in conjunction with clinical findings can be considered a strong predictor of a neoplastic process.

Hürthle cells in fine-needle aspirates of the thyroid: a review of their diagnostic criteria and significance

Although the cytological assessment of Hürthle cell lesions is challenging, the literature offers good, albeit imperfect, guidance to aid in the crucial distinction between nonneoplastic and neoplastic lesions. The significance of a cytologic diagnosis of follicular neoplasm, Hürthle cell type, lies in the rate of malignancy on follow-up surgical excision, ranging in the literature from 10% to 45%. A cytodiagnosis of atypia of undetermined significance (AUS), Hürthle cell type, appears to be associated with a lower risk of malignancy on follow-up than other subtypes of AUS; however, this area warrants further investigation.

Hürthle cell neoplasms diagnosed by fine needle aspiration are not associated with an increased risk of malignancy

OBJECTIVES

The aim of this study is to determine the risk of neoplasm and malignancy in thyroid fine needle aspiration (FNA) diagnosed as atypia of undetermined significance with Hürthle cell change (AUS-H) or Hürthle cell neoplasm (HCN).

STUDY DESIGN

A computerized search of our laboratory information system was performed to identify all thyroid FNA and correlating surgical pathology diagnoses including Hürthle cell or oncocyte in the diagnostic nomenclature. The risks of neoplasm and malignancy were calculated for AUS-H and HCN categories separately.

RESULTS

For the 29 AUS-H cases, the follow-up histology demonstrated 15 benign lesions, 4 follicular adenomas, 7 Hürthle cell adenomas, 1 papillary microcarcinoma (PMC), 1 follicular carcinoma and 1 Hürthle cell carcinoma. For the 93 HCN cases, the follow-up histology demonstrated 28 benign lesions, 9 follicular adenomas, 32 Hürthle cell adenomas, 2 PMCs, 2 papillary thyroid carcinomas, 6 follicular carcinomas and 14 Hürthle cell carcinomas.

CONCLUSIONS

The risks of neoplasm and malignancy were 62 and 7% for the AUS-H category and 73 and 24% for the HCN category, respectively. The risk of malignancy for the AUS-H patients is within the 5- to 15-percent range suggested by the Bethesda System for Reporting Thyroid Cytology and within the 15- to 30-percent range suggested for follicular neoplasms.

Should "indeterminate" diagnoses be used for thyroid fine-needle aspirates of nodules smaller than 1 cm?

CONTEXT

The Bethesda System for thyroid fine-needle aspirates does not account for the size of the lesion that is aspirated.

OBJECTIVE

To determine whether the size of the lesion would be helpful in order to reduce indeterminate thyroid aspirations.

DESIGN

We correlated the results of all thyroid aspirations and surgical resection for the last 16 years at our institutions.

RESULTS

A total of 9080 cases were aspirated and 1393 resections were performed. Of those resected, a total of 236 (17%) were classified as atypical follicular cells of undetermined significance, and 256 (18%) were classified as suspicious for a follicular/Hürthle cell neoplasm. A total of 52 incidental papillary carcinomas were identified in these indeterminate cases at resection (52 of 492; 11%). Thirty-seven (16%) atypical follicular cells of undetermined significance cases and 21 (8%) suspicious for a follicular/Hürthle cell neoplasm cases were for nodules smaller than 1 cm in diameter. When cases subtyped as atypical, a papillary carcinoma cannot be ruled out, were removed (13 cases), the remaining 24 and 21 aspirates identified 3 tumors each (13% and 14%), all papillary carcinomas. Together, the incidence of identified carcinomas was not significantly different than that of incidental carcinomas (13% versus 11%, P = .48). The rate of identified carcinomas was significantly less than for similar indeterminate cases smaller than 1 cm (excluding cases of atypical, papillary carcinoma cannot be ruled out) (88 of 330 cases; 27%; P = .05).

CONCLUSIONS

For nodules smaller than 1 cm in our series, indeterminate aspirates without features of papillary carcinomas have the same risk of malignancy as benign aspirates.

The cytologic category of oncocytic (Hurthle) cell neoplasm mostly includes low-risk lesions at histology: an institutional experience

DESIGN

The cytological diagnosis of oncocytic/Hurthle cell neoplasms (OCN) represents a challenge with which cytopathologists face up to in their practice. The majority of these lesions undergo surgery for a definitive characterization of the nature mainly due to their more aggressive behavior than other malignant follicular lesions. In this study, we aimed at the evaluation of the effective malignant rate in a large cohort of OCNs.

METHODS

From January 2008 to December 2011, we analyzed 150 cyto-histological OCNs and 64 benign oncocytic/Hurthle lesions (BOL). Both groups of patients were analyzed for clinical and cyto-histological parameters. All the nodules were sampled under sonographic guidance and processed with the liquid-based cytological method.

RESULTS

In agreement with literature, we found a significant correlation only with female gender in both OCN (P=0.0160) and BOL groups. The 64 BOLs were histologically diagnosed as 15 Hashimoto thyroiditis (HT), 45 hyperplastic nodules in HT, and four papillary thyroid carcinomas (PTC, 6.2%). The 150 OCNs resulted in 141 (94%) oncocytic adenomas and nine (6%) malignant lesions. The latter group included five oncocytic carcinomas (OCC), three oncocytic variants of PTC, and one macrofollicular PTC featured by mild nuclear clearing with a dispersive cellular pattern. The malignant rate was respectively 6.2% in BOLs without any OCC whereas 3.3% OCC diagnosed in the OCN category.

CONCLUSIONS

Our OCNs mostly resulted in histological adenomas with a lower rate of malignancy than in other series. Some morphological parameters (nuclear clearing, dysplasia, and dispersive cellular pattern) might be helpful in stratifying OCN patients into different risks of malignancy.

Subclassification of "atypia of undetermined significance" in thyroid fine-needle aspirates

To identify the subtypes of atypia of undetermined significance (AUS) that confers a different magnitude for the risk of malignancy (RM), thyroid fine-needle aspiration (FNA) cases carrying a diagnosis of "atypical follicular cells" or "follicular lesion" with surgical pathology followup were included in this study. The direct smears of the aspirates were rereviewed and subclassified into four subgroups based on cytomorphology: AUS cannot exclude follicular neoplasm (AUS-FN), AUS cannot exclude Hürthle cell neoplasm (AUS-HCN), AUS cannot exclude papillary carcinoma (AUS-PTC) and AUS, not otherwise specified (AUS-NOS). Based on the followup histopathologic findings, RM not including papillary microcarcinoma (PMC), RM including PMC and the risk of neoplasm (RN) were calculated for each of the four AUS subgroups. A total of 138 AUS cases were subclassified into AUS-NOS (48), AUS-PTC (41), AUS-FN (32), and AUS-HCN (17). RM not including PMC was 32% for AUS-PTC (P < 0.001), 25% for AUS-FN, 8% for AUS-NOS, 0% for AUS-HCN, and 18% for all AUS cases. RM including PMC was 54% for AUS-PTC (P < 0.001), 34% for AUS-FN, 19% for AUS-NOS, 18% for AUS-HCN, and 33% for all AUS cases. RN was 63% for AUS-PTC (P = 0.05), 81% for AUS-FN (P < 0.01), AUS-HCN 53%, AUS-NOS 44% and 59% for all cases. In our study, subclassification enabled us to further divide AUS cases into high- and low-risk groups. The high-risk group includes AUS-PTC with a significantly higher risk of malignancy and AUS-FN with a significantly higher risks of neoplasm. AUS-HCN and AUS-NOS subgroups demonstrate a lower risk of malignancy of <10%.

Oncocytic follicular nodules of the thyroid with or without chronic lymphocytic thyroiditis: An institutional experience

BACKGROUND

Oncocytic follicular (OF) cells can be a prominent component of fine needle aspiration (FNA) specimens from neoplasms (adenomas and carcinomas) and nodules arising in multinodular goiter and chronic lymphocytic thyroiditis (CLT). Because OF cells can be present in non-neoplastic and neoplastic thyroid lesions it can be challenging to differentiate between these two in FNA specimens. The aims of this study were to determine the risk of malignancy in cases diagnosed as either oncocytic follicular neoplasm (OFN) or hyperplastic/adenomatoid nodule with OF on FNA and to identify clinicopathologic features that may help in predicting malignancy in such cases, especially the presence or absence of CLT.

DESIGN

We retrospectively searched the computerized laboratory information system at our institution between 1998 and 2009 for thyroid US guided FNA specimens in which the term "oncocytic/oncocytes" was mentioned in the final cytopathologic diagnosis. A total of 340 cases were selected for this study. The following data points were collected: Patient demographics, site of thyroid biopsy, size of lesion, FNA diagnosis, histopathologic follow-up and presence of CLT. Surgical pathology follow-up (SPFU) was available in 269 (79%) cases.

RESULTS

Two hundred and sixty patients were females and 80 males (average age 53 years). The lesion size was <3.0 cm in 241 (71%) and ≥ 3.0 cm in 99 (29%) cases. Cytologic diagnoses included: Follicular neoplasm with oncocytic features (FNOF) 321 and suggestive of FNOF 19 cases; a secondary cytologic diagnosis of CLT was made in 20 cases. SPFU was available in 269 (79%) cases; it was benign in 213 (213/267 = 79%) and malignant in 56 (56/269 = 21%) cases. The background thyroid showed CLT in 67 (25%) cases; 24% (48/196) neoplasms occurred with versus 76% (147/196) without CLT. The rate of malignancy was lower in nodules measuring less than 3.0 cm as compared to those equal or greater than 3.0 cm in size (17% vs. 28% respectively). The presence of CLT did not significantly alter the rate of malignancy in both FNA and surgical pathology specimens.

CONCLUSIONS

Based on this study, nodule size and not CLT appears to be an important clinicopathologic features in the management of thyroid FNA specimens diagnosed as OFN.

Can abundant colloid exclude oncocytic (Hürthle cell) carcinoma in thyroid fine needle aspiration? Cytohistological correlation of 127 oncocytic (Hürthle cell) lesions

OBJECTIVE

The objective of the present study was to find out whether the presence or absence of certain cytological features can exclude oncocytic (Hürthle cell) carcinoma in thyroid fine needle aspiration (FNA) to minimize unnecessary surgery.

METHODS

Over a 17-year period, 127 hypercellular, oncocyte-exclusive, lymphocyte-absent aspirates obtained via ultrasound-guided FNA with on-site assessment had histology slides for review. The presence or absence of six cytological features (microfollicular arrangement, discohesive single cells, small cell dysplasia, large cell dysplasia, transgressing blood vessels and colloid) and one histological feature (macrofollicular component) were determined for each case independently by two cytopathologists.

RESULTS

Histology showed 12 (9.4%) cases of Hashimoto thyroiditis, 23 (18.1%) oncocytic adenomatoid nodules in nodular goitre, 66 (52.0%) oncocytic adenomas and 26 (20.5%) oncocytic carcinomas (13 minimally invasive without angioinvasion, six minimally invasive with angioinvasion, seven widely invasive). Histologically, a macrofollicular component was present in seven of 26 (26.9%) oncocytic carcinomas, including one case with abundant thin colloid. A microfollicular arrangement, discohesive single cells, small cell dysplasia, large cell dysplasia and transgressing vessels were present in oncocytic carcinoma, oncocytic adenoma and oncocytic adenomatoid nodules in nodular goitre.

CONCLUSIONS

A macrofollicular component is frequently present in oncocytic carcinoma, oncocytic adenoma and oncocytic adenomatoid nodules in nodular goitre. None of the cytological features studied, including abundant colloid, can exclude oncocytic carcinoma. Oncocytic carcinoma can only be excluded by thorough histological examination of thyroidectomy specimens. A molecular marker is needed to triage oncocytic lesions in thyroid FNA.

Eliminating the "Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance" category from the Bethesda System for Reporting Thyroid Cytopathology

The "Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/FLUS)" category in the Bethesda System for Reporting Thyroid Cytology is heterogeneous and includes both specimens with borderline cellularity/compromised quality and those with genuine atypia. We have used a reporting scheme that is similar to the Bethesda System but does not include an AUS/FLUS category. We retrospectively reviewed all reports on thyroid FNA and thyroidectomy specimens submitted to the Beth Israel Deaconess Medical Center from January 2006 to December 2008. The positive predictive values for various categories and subcategories in this scheme demonstrate that the AUS/FLUS category can be eliminated to provide information for the most appropriate management of patients with thyroid nodules.

The significance of hurthle cells in thyroid disease

Hürthle cells (HCs) and HC change, along with the frequently employed synonyms "oncocytes/oncocytic change" or "oxyphils/oxyphilic change," are not infrequently described on fine-needle aspiration biopsy (FNAB) reports of thyroid lesions. The description of HCs on FNAB reports may cause significant concern to the clinician; however, placing the finding in the appropriate clinical context may alleviate some anxiety. Not all oxyphilic cells are true HCs and not every aspirate containing HCs is or should be considered equivalent to an HC neoplasm (HCN). There are many benign thyroid lesions associated with HCs or HC change. For clinicians, it may be difficult to discern the significance of these findings and to determine an appropriate course of action. A skilled and experienced cytopathologist is invaluable in discriminating the subtle features that distinguish these lesions from those warranting a more aggressive approach. The diagnosis of HC carcinoma relies on histopathologic scrutiny and evidence of capsular and/or vascular invasion or metastasis to lymph nodes or distant organs. Many investigators have sought clinical, radiographic, cytological, genetic, and other factors to attempt to discriminate preoperatively between benign and malignant HCNs. To date, none have been definitively proven to be reliable. For now, because of the inability to determine the benign or malignant nature of such neoplasms based on cytology alone, a surgical approach is warranted.

The Bethesda system for reporting thyroid cytopathology: An experience of 1,382 cases in a community practice setting with the implication for risk of neoplasm and risk of malignancy

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) has provided a set of uniform diagnostic terminology including benign (B), atypia of undetermined significance (AUS), follicular neoplasm (FN), suspicious for malignancy (SM), malignancy (M), and nondiagnostic (ND) for the interpretation of thyroid fine-needle aspiration (FNA). We applied this terminology on our 1,382 thyroid aspirates in a community practice setting, which included 539 cases of B (39%), 376 cases of AUS (27.2%), 116 cases of FN (8.4%), 37 cases of malignant (2.7%), 36 cases of SM (2.6%), and 278 cases of ND (20.1%). Two hundred twenty-one cases (16%) of thyroid FNA had corresponding follow-up thyroidectomies. Each diagnostic category represented a unique association with risk of malignancy and risk of neoplasm. Based on histologic follow-up, the risk of neoplasm (including benign and malignant neoplasm) was B 14%, AUS 44%, FN 67%, SM 77%, and M 100% and the risk of malignancy was B 3%, AUS 6%, FN 22%, SM 56%, and M 100%. The classification and follow-up recommendation of TBSRTC are appropriate for each category. Both B and AUS are low-risk lesions with low probability of malignancy. FN predicts a higher rate for neoplasm but an intermediate rate for malignancy while SM carries a high risk for malignancy.

Subclassification of atypical cells of undetermined significance in direct smears of fine-needle aspirations of the thyroid: distinct patterns and associated risk of malignancy

BACKGROUND

Atypical cells of undetermined significance (AUS) in thyroid fine-needle aspirates (FNAs) may have poor interobserver agreement. Some authors have suggested that "atrophic" microfollicles should be diagnosed as benign. This laboratory sought to determine whether criteria for this diagnosis could be improved by subcategorizing cases into specific patterns, including the atrophic pattern, and determining their risk of malignancy.

METHODS

A series of 7089 FNAs were reviewed and correlated with subsequent resection specimens. Cases of AUS were reviewed and subclassified.

RESULTS

Cases could be subcategorized into the following categories: 1) atypical, papillary carcinoma cannot be ruled out, 2) atypical, Hürthle cell neoplasm can not be ruled out, 3) cellular atrophic pattern, 4) scant atrophic pattern, and 5) cytologic atypia alone. Cytologic atypia alone (50%) and both atrophic patterns (21% and 34%) had a significant risk of malignancy.

CONCLUSIONS

The majority of AUS cases in thyroid FNA can be subcategorized into 5 different patterns, all with associated significant risk of malignancy. "Atrophic" microfollicles are a significant risk factor for malignancy and should not be diagnosed as benign on the basis of lack of cytologic atypia.

Cytomorphological features of Hürthle cell carcinoma: A report of two cases with review of literature

The use of the term “Hürthle cell neoplasm” as the gold standard should be discouraged as it makes evaluating these lesions more confusing. Recently, a number of studies have been conducted to define criteria that are more specific for Hürthle cell carcinoma (HCC). We herein report two cases of HCC of thyroid which were accurately diagnosed preoperatively using various cytological features described in the recent studies. A review of the literature is also presented.

Should "atypical follicular cells" in thyroid fine-needle aspirates be subclassified?

BACKGROUND

Recently reported Bethesda terminology suggests the use of the term "atypical follicular cells" for thyroid fine-needle aspirates. Previous work has suggested that some types of "atypical follicular cells" have different risks of malignancy.

METHODS

The author reviewed the results of all thyroid aspirations with surgical resection performed during the past 13 years at our institution, subclassified the "atypical follicular cells," and compared their relative risk of malignancy.

RESULTS

During the 13 years in question, a total of 7089 cases were aspirated with 1331 resections. A total of 548 (14%) of all cases were classified as "atypical follicular cells," and 204 (37%) were resected with an overall risk of malignancy of 25%. The risk of malignancy for atypical follicular cells subclassified as "rule out papillary carcinoma" was significantly higher (38%) than the other atypical cells. The risk of "rule out Hurthle cell neoplasm" was, at 7%, significantly lower than the other cases of atypical follicular cells (P<.001 and P<.02, respectively).

CONCLUSIONS

Different types of "atypical follicular cells" have significantly different risks of malignancy. This disparity of risk should be communicated by the cytologist.

Tumor size and age predict the risk of malignancy in Hürthle cell neoplasm of the thyroid and can therefore guide the extent of initial thyroid surgery

BACKGROUND

The majority of patients having a diagnosis of Hürthle cell neoplasm (HCN) on fine-needle aspiration (FNA) of a thyroid nodule have a diagnostic thyroid lobectomy to make the final diagnosis. If the nodule is malignant, they require a completion thyroidectomy. The objective of this study was to devise a simple clinical scheme capable of predicting malignancy in patients with cytologic diagnosis of HCN and, therefore, guide the extent of initial thyroid surgery.

METHODS

A total of 57 patients who underwent thyroid surgery after an FNA diagnosis of HCN were retrospectively studied. The patients were examined for clinical features, preoperative imaging studies, and pathology reports. The risk of malignancy was calculated using a multiple logistic regression model.

RESULTS

The overall rate of malignancy in patients with HCN was 46% (26/57). The predictors of malignancy based on multiple logistic regression analysis were tumor size >1.5 cm (odds ratio [95% confidence interval] = 8.0 [1.9-33.4]) and patient age >45 years (odds ratio [95% confidence interval] = 2.3 [0.6-8.6]). In patients with nodules larger than 1.5 cm, the predicted probability of malignancy was greater in patients over 45 years than in younger patients (65% for >45 years vs. 44% for ≤45 years). In patients with a nodule 1.5 cm or less, the probability of malignancy was relatively low and not significantly different between the two age categories (18% for >45 years vs. 10% for ≤45 years).

CONCLUSIONS

This study suggests that tumor size and age can be integrated into decision making for patients with an FNA diagnosis of HCN to facilitate patient selection for surgical referral and, particularly, to determine in which patients a thyroidectomy rather than a lobectomy should be the initial surgery.

Clinical and cytological features predictive of malignancy in thyroid follicular neoplasms

BACKGROUND

The preoperative diagnosis of malignancy in nodules suspicious for a follicular neoplasm remains challenging. A number of clinical and cytological parameters have been previously studied; however, none have significantly impacted clinical practice. The aim of this study was to determine predictive characteristics of follicular neoplasms useful for clinical application.

METHODS

Four clinical (age, sex, nodule size, solitary nodule) and 17 cytological variables were retrospectively reviewed for 144 patients with a nodule suspicious for follicular neoplasm, diagnosed preoperatively by fine-needle aspiration (FNA), from a single institution over a 2-year period (January 2006 to December 2007). The FNAs were examined by a single, blinded pathologist and compared with final surgical pathology. Significance of clinical and cytological variables was determined by univariate analysis and backward stepwise logistic regression. Odds ratios (ORs) for malignancy, a receiver operating characteristic curve, and predicted probabilities of combined features were determined.

RESULTS

There was an 11% incidence of malignancy (16/144). On univariate analysis, nodule size >OR=4.0 cm nears significance (p = 0.054) and 9 of 17 cytological features examined were significantly associated with malignancy. Three variables stay in the final model after performing backward stepwise selection in logistic regression: nodule size (OR = 0.25, p = 0.05), presence of a transgressing vessel (OR = 23, p < 0.0001), and nuclear grooves (OR = 4.3, p = 0.03). The predicted probability of malignancy was 88.4% with the presence of all three variables on preoperative FNA. When the two papillary carcinomas were excluded from the analysis, the presence of nuclear grooves was no longer significant, and anisokaryosis (OR = 12.74, p = 0.005) and presence of nucleolus (OR = 0.11, p = 0.04) were significantly associated with malignancy. Excluding the two papillary thyroid carcinomas, a nodule size >or=4 cm, with a transgressing vessel and anisokaryosis and lacking a nucleolus, has a predicted probability of malignancy of 96.5%.

CONCLUSIONS

A combination of larger nodule size, transgressing vessels, and specific nuclear features are predictive of malignancy in patients with follicular neoplasms. These findings enhance our current limited predictive armamentarium and can be used to guide surgical decision making. Further study may result in the inclusion of these variables to the systematic evaluation of follicular neoplasms.

Diagnostic terminology and morphologic criteria for cytologic diagnosis of thyroid lesions: a synopsis of the National Cancer Institute Thyroid Fine-Needle Aspiration State of the Science Conference

The National Cancer Institute (NCI) sponsored the NCI Thyroid Fine-needle Aspiration (FNA) State of the Science Conference on October 22-23, 2007 in Bethesda, MD. The two-day meeting was accompanied by a permanent informational website and several on-line discussion periods between May 1 and December 15, 2007 (http://thyroidfna.cancer.gov). This document summarizes matters regarding diagnostic terminology/classification scheme for thyroid FNA interpretation and cytomorphologic criteria for the diagnosis of various benign and malignant thyroid lesions. (http://thyroidfna.cancer.gov/pages/info/agenda/).

Fine-needle aspiration biopsy of Hurthle cell lesions of the thyroid gland: A cytomorphologic study of 139 cases with statistical analysis

BACKGROUND

Lesions of the thyroid gland composed of Hurthle cells encompass pathologic entities ranging from hyperplastic nodules with Hurthle cell metaplasia to Hurthle cell carcinomas. The cytologic distinction between these entities can be diagnostically challenging. Many cytologic features of Hurthle cell lesions that distinguish neoplastic Hurthle cell lesions requiring surgery from those that are benign and nonneoplastic have been described, but with variable usefulness. This is due, in part, to the small numbers of cases examined in previous studies and the limited application of statistical analysis. A morphologic study was made of 139 Hurthle cell lesions of the thyroid gland and statistical analysis applied to identify a set of cytomorphologic features that distinguish benign Hurthle cell lesions (BHCL) from Hurthle cell neoplasms (HCN).

METHODS

Fine-needle aspiration biopsies (FNABs) of thyroid nodules with a predominant Hurthle cell component and corresponding histologic followup were included in the study. Cases were divided into BHCL and HCN groups on the basis of the histologic diagnosis. All cases were reviewed to assess the following 14 cytologic features: overall cellularity, cytoarchitecture, percentage of Hurthle cells, percentage of single cells, percentage of follicular cells observed as naked Hurthle cell nuclei, background colloid, chronic inflammation, cystic change, transgressing blood vessels (TBV), intracytoplasmic lumina, presence of multinucleated Hurthle cells, nuclear to cytoplasmic ratio, nuclear pleomorphism/atypia, and nucleolar prominence. The results were evaluated by using univariate and stepwise logistic regression (SLR) analysis; statistical significance was achieved at P-values < 0.05.

RESULTS

One hundred thirty-nine FNAB specimens, corresponding to 56 HCN and 83 BHCL, fulfilled the study criteria. Six of the 14 cytologic features evaluated were shown by univariate analysis to be statistically significant in predicting HCN: nonmacrofollicular architecture (P < 0.001), absence of background colloid (P < 0.001), absence of chronic inflammation (P < 0.001), presence of TBV (P < 0.001), > 90% Hurthle cells (P < 0.001), and >10% single Hurthle cells (P = 0.014). The first four of these features were also shown to be statistically significant in the SLR analysis (P = 0.005, 0.010, 0.016, and 0.045, respectively), and when all four of these features were present HCN was correctly identified 86% of the time.

CONCLUSIONS

In the current study of 139 FNAB specimens of thyroid Hurthle cell nodules, 14 cytologic features were examined and 6 were found to be statistically significant in identifying HCN. The following four features, when found in combination, were found to be highly predictive of HCN: nonmacrofollicular architecture, absence of colloid, absence of inflammation, and presence of TBV.

Fine-needle aspiration of papillary thyroid carcinoma: distinguishing between cases that performed well and those that performed poorly in the College of American Pathologists Nongynecologic Cytology Program

CONTEXT

Although the cytologic features of papillary thyroid carcinoma in fine-needle aspiration specimens are well known, the correlation of these features with the ability of cytologists to identify this tumor has not been well studied.

OBJECTIVE

To compare the cytologic features of cases of papillary thyroid carcinoma that performed poorly with those of cases that performed well.

DESIGN

The cytologic features of 13 cases of papillary thyroid carcinoma from the College of American Pathologists Nongynecologic Cytology Program that performed poorly were compared with those of 15 cases that performed well.

RESULTS

Compared with cases that performed well, cases that performed poorly were significantly more likely to lack marked nuclear enlargement (38% vs 100%, P < .001), lack pale chromatin (8% vs 47%, P = .04), and lack intranuclear inclusions (8% vs 53%, P = .02). The differences between the 2 groups in staining, type of preparation, nuclear grooves, nuclear crowding, colloid, cellularity, nuclear pleomorphism, and Hurthle cell change were not significant.

CONCLUSIONS

Cases of papillary thyroid carcinoma that lack marked nuclear enlargement, pale chromatin, and intranuclear inclusions are significantly more difficult to recognize than cases that have these features. Increased awareness of these types of cases might improve the performance of thyroid fine-needle aspiration in clinical practice.

Interobserver Agreement on Microfollicles in Thyroid Fine-Needle Aspirates

Context.—Although microfollicles are a well-known feature of follicular neoplasms in fine-needle aspirates of the thyroid, the level of agreement about classifying groups as microfollicles is not known.

Objective.—To determine what features are present in groups that are consistently classified as microfollicles.

Design.—We showed 45 small groups of follicular cells each composed of fewer than 50 cells from fine-needle aspirates of the thyroid to 12 members of the College of American Pathologists Cytopathology Committee, who then classified the groups into microfollicles, macrofollicles, and indeterminate groups.

Results.—Twenty groups were consistently classified as microfollicles, 7 groups as macrofollicles, and 18 groups as indeterminate. Cases that were consistently classified as microfollicles were composed of fewer than 15 cells (19/ 20 cases), were arranged in a circle with a lumen (13/20 cases) that was at least two-thirds complete (12/20 cases), and were flat (18/20 cases). Cases that were classified as macrofollicular had between 8 and 35 cells, were arranged in sheets composed of at least 15 cells (5/7 cases) or rows of 8 cells (2/7 cases), and were flat (7/7 cases). In contrast, cases that were indeterminate were composed of either 3-dimensional groups (5/18 cases), flat groups of fewer than 10 cells (11/18 cases), or single cells (1/18 cases).

Conclusion.—Not all small groups of follicular cells are consistently classified as microfollicles, and some are more often classified as macrofollicles. The criteria described here for reproducible microfollicles (&lt;15 cells, arranged in a circle that is at least two-thirds complete, and flat) may help improve the agreement in classification of microfollicles and lead to more consistent classification of thyroid fine-needle aspirates.

Fine-needle aspiration biopsy specimen with a predominance of Hürthle cells: A dilemma in the management of nodular thyroid disease

BACKGROUND

A fine-needle aspiration biopsy (FNAB) specimen of a thyroid nodule with a predominance of Hürthle cells usually is indicative of a Hürthle cell neoplasm, but it also may occur with nonneoplastic disease.

METHODS

A prospective nodular thyroid disease database was used to identify patients with a FNAB specimen consisting of a predominance of Hürthle cells. Clinical factors were investigated and FNAB specimens were examined in a blinded fashion by a single cytopathologist to determine if there were specific factors that could be used to distinguish nonneoplastic from neoplastic disease.

RESULTS

Of the 738 patients with nodular thyroid disease, 622 had a FNAB specimen. The FNAB specimen was interpreted as consistent with a Hürthle cell neoplasm in 45 (7%) patients, 7 (16%) with carcinoma, 21 (47%) with adenoma, 12 (27%) with adenomatous hyperplasia, and 5 (11%) with thyroiditis. Extensive cellularity and absent colloid were associated with neoplastic disease (P < .05). No cytologic feature reliably excluded neoplastic disease (P > .05). No significant differences in age (x +/- SD) (51 +/- 17 vs 54 +/- 17 y), sex (female/male ratio, 6/1 vs 15/2), nodule size (3.9 +/- 1.9 vs 3.4 +/- 2.0 cm), weight of excised thyroid tissue (42 +/- 27 vs 33 +/- 30 g), or functional status of the thyroid gland was observed between patients with neoplastic (n = 28, 62%) versus nonneoplastic (n = 17, 38%) disease.

CONCLUSIONS

Neoplastic disease accounts for two thirds of the pathology in patients with a predominance of Hürthle cells on FNAB specimen and neither clinical nor cytologic features reliably exclude Hürthle cell adenoma or carcinoma. As a result, thyroidectomy is recommended for all patients with a thyroid nodule and a predominance of Hürthle cells on FNAB specimen.

"Atypical" cells in fine-needle aspiration biopsy specimens of benign thyroid cysts

BACKGROUND

Cystic lesions of the thyroid are common. Most are benign nodules with degenerative changes in a multinodular goiter. Fine-needle aspiration biopsy (FNAB) specimens from these cystic nodules usually are easily interpreted as benign. However, occasionally, cells with atypical features are encountered, increasing the possibility of a cystic malignant neoplasm. To the authors' knowledge, the microscopic features of these benign cells, presumed to be of cyst-lining origin, have not been well described to date. To refine the description of their morphologic features, with the belief that better recognition will avoid unnecessary surgery, the authors examined the cytologic and corresponding histologic features of thyroid cysts with "atypical" cells.

METHODS

A total of 149 FNAB specimens from thyroid cysts containing atypical cells were identified. Seventy-five specimens with subsequent histologic correlation showing a benign cystic thyroid nodule were selected for study. The cytologic features of the atypical cyst-lining cells were reviewed and correlations were made with histologic, immunohistochemical, and clinical features. In addition, 12 FNAB specimens of histologically proven cystic papillary carcinoma diagnosed as atypical were reviewed for comparison.

RESULTS

The majority of specimens (94%) were diagnosed cytologically as atypical thyroid cysts. However, in 29% of these specimens, a papillary or Hurthle cell neoplasm could not be excluded. The cytologic features of the atypical cells most often resembled classic reparative epithelial cells consistent with a cyst-lining origin. The most common features were cohesive flat sheets (84%), distinct cell borders (96%), nuclear enlargement (92%), nuclear grooves (79%), dense granular cytoplasm (79%), small distinct nucleoli (85%), fine chromatin (87%), and elongate to spindled cytomorphology (57%). In contrast to the atypical cells from benign cysts, cystic papillary carcinomas lacked the repair-like spindled cytomorphology, and showed nuclear crowding (100%), as well as papillary microarchitecture (50%), and rare intranuclear pseudoinclusions (42%). Histologically, the atypical cells in aspirate specimens corresponded to cyst-lining cells, which exhibited a spectrum ranging from flattened elongate cells with eosinophilic cytoplasm to more polygonal cells with abundant eosinophilic cytoplasm, enlarged irregular nuclei with pale chromatin, prominent nuclear grooves, and distinct nucleoli. Immunohistochemical staining of a subset of the resected thyroid cysts showed that the cyst-lining cells were positive for keratin and thyroglobulin, consistent with thyroid follicular cells.

CONCLUSIONS

Atypical cyst-lining cells were found to have characteristic features (e.g., distinct cell borders, elongated shape, eosinophilic cytoplasm, and distinct nucleoli) and lacked nuclear crowding, intranuclear pseudoinclusions, and papillary architecture that, in many specimens, allowed them to be recognized as benign. The authors recommended that the subset of cells with the characteristic features described in the current study be reported as "consistent with benign cyst lining cells".

Fine-Needle Aspiration of Thyroid Nodules: Past, Present, and Future

OBJECTIVE

To present a review of the traditional and more recent techniques and applications of thyroid fine-needle aspiration biopsy.

METHODS

We describe the cytologic features and differential diagnoses of various thyroid lesions, outline recommendations for diagnostic categories, and discuss new techniques that have shown some promise in the diagnosis of thyroid nodule fine-needle aspiration specimens.

RESULTS

Fine-needle aspiration biopsy of the thyroid has proved to be an excellent diagnostic tool in the initial management of thyroid nodules. Numerous studies have shown its high sensitivity and specificity in diagnosing malignant tumors of the thyroid, especially papillary thyroid carcinoma. As with other diagnostic tests, however, its effectiveness is highly dependent on the expertise of the operator performing the procedure and the adequacy of the specimen for interpretation of the cytomorphologic features. On-site evaluation of thyroid specimens promotes adequate specimen sampling and reduces the incidence of nondiagnostic specimens. Diagnostic reports on thyroid fine-needle aspiration should include patient demographics and pertinent clinical history, site and size of the thyroid nodule, mode of aspiration, number of needle passes, assessment of specimen adequacy, diagnosis, and recommendations. Although immunohistochemical and molecular markers have received considerable attention recently, additional studies are needed before they can be used to separate benign from malignant follicular thyroid lesions.

CONCLUSION

Overall, fine-needle aspiration biopsy of thyroid nodules has proved to be sensitive, specific, and well accepted by patients because of minimal discomfort and complications.