Interobserver variability in the fine needle aspiration biopsy diagnosis of follicular lesions of the thyroid gland

OBJECTIVE: To study the degree of interobserver variability in the interpretation of fine needle aspiration (FNA) biopsies of the thyroid, specifically in the categorization of follicular lesions (FLs), and to examine the accuracy of FNA diagnosis of FLs with surgical follow-up. STUDY DESIGN: Fifty cases were chosen with surgical follow-up and a cytologic diagnosis of either FL (21) or follicular neoplasms (29). Representative slides were selected for each case and circulated to 4 pathologists for review. Interobserver variability was assessed using pairwise K statistics. Accuracy of the cytologic diagnoses in predicting a nonneoplastic or neoplastic outcome was determined by measuring sensitivity and specificity. Likelihood ratios and receiver operator characteristic curves were calculated for each reviewer. RESULTS: Interobserver agreement between the 4 pathologists was fair to substantial (K scores, 0.199-0.617). The accuracy of the 4 pathologists' cytologic diagnoses in predicting the surgical outcome was 77-90% for follicular neoplasms and 53-74% for nonneoplastic diagnoses. CONCLUSION: FLs present diagnostic difficulties as to cytologic categorization. A wide range of interobserver agreement was found in this study of 4 pathologists from the same institution. Some pathologists make greater use of intermediate categories, such as FL, favor nonneoplastic, or FL, favor neoplastic, whereas others show more definitive categorization into benign and neoplastic groups.     

Galectin-3 is not useful in thyroid FNA

INTRODUCTION: Previous studies have suggested that galectin-3 immunohistochemistry may be useful in the fine needle aspiration (FNA) diagnosis of thyroid carcinoma as it has been reported to selectively stain carcinomas and not adenomas or goitres. METHODS: Fifty-one patients were included in a prospective study of galectin-3 in thyroid FNA; 88.2% were female and 11.8% male, mean age 53 years, range 25-87 years. Cell blocks were prepared and stained for galectin-3 if any cells were present in needle washings from the respective FNAs. RESULTS: Twelve of 51 (23.5%) of cell blocks contained epithelial cells. One benign and one inadequate FNA were negative for galectin-3 staining. One of five non-diagnostic FNA cases, a papillary carcinoma on final histology showed positive staining. Four follicular neoplasm/suspicious of carcinoma cases showed negative staining. One malignant FNA case, a papillary carcinoma showed positive staining with galectin-3 but three further carcinomas, two papillary and one follicular were galectin-3 negative. CONCLUSION: Galectin-3 immunohistochemistry does not appear to be a useful adjunct to diagnosis in thyroid FNA as it does not reliably distinguish malignant and benign lesions. Many thyroid aspirates are of low cellularity and are not suitable for cell block immunohistochemistry.     

Usefulness of fine needle aspiration of the thyroid in an endemic goiter region

The accuracy of fine needle aspiration (FNA) cytology of the thyroid was addressed in 142 nodular goiters from an endemic goiter region. The aspirations and their interpretation were based on the methodology of the Karolinska Hospital. For practical purposes, the follicular lesions were divided into type I (benign), type II (atypical benign) and type III (suspicious). Excluding the follicular lesions, the cytohistologic agreement for the whole series was 87%, with a correlation of 81.5% for carcinomas. The type I and type II follicular lesions were benign on histologic grounds; 39% of the carcinomas were detected in the type III follicular lesions. The 0.7% false-positive diagnoses increased to 15% when type III follicular lesions were included. No false negatives were recorded. These observations, together with the increase of surgically resected thyroid carcinomas after FNA was accepted as a diagnostic modality, indicate that FNA biopsy of the thyroid is an accurate diagnostic method and is useful in selecting patients for subsequent surgery in areas of endemic goiter.     

Clinicopathologic analysis of fine needle aspiration cytology of the thyroid. A review of 1,613 cases and correlation with histopathologic diagnoses

OBJECTIVE: To evaluate the accuracy of fine needle aspiration (FNA) of thyroid lesions at our institution and to ascertain its usefulness in determining the therapeutic approach. STUDY DESIGN: The authors reviewed the results of 1,613 cases of FNA cytology of thyroid nodules performed from 1999 to 2001 at the Department of Pathology, Chonnam National University Hospital. Cytologic diagnoses were compared with histologic diagnoses in 207 cases that included both FNA and thyroid surgery. RESULTS: The sensitivity for the detection of neoplasms (carcinoma and follicular adenoma) was 78.4% and the specificity 98.2%. A false positive diagnosis was made in 1 case (1.8%) and false negative ones in 28 cases (21.5%). The diagnostic accuracy was 84.4%, with a positive predictive value of 99.0% and negative predictive value of 66.3%. The predictive value of a cytologic diagnosis was 100% in papillary carcinoma. CONCLUSION: FNA is a useful test in determining the therapeutic approach of thyroid lesions.     

Fine needle aspiration cytology of head and neck masses. Seven years' experience in a secondary care hospital

OBJECTIVE: To study the value of fine needle aspiration (FNA) in the diagnosis of head and neck masses in a secondary care hospital. STUDY DESIGN: FNA from 225 patients with head and neck masses were reviewed. The results were analyzed, according to anatomic location, into 3 groups: inflammatory, congenital and neoplastic. FNA diagnoses were retrospectively correlated with available histologic findings or with the outcome of treatment. Accuracy, sensitivity, specificity, positive predictive value and negative predictive value in the diagnosis were computed. The numbers of lymph node biopsies performed before and after introduction of the procedure were compared. RESULTS: The most common diagnoses were reactive/nonspecific lymphadenitis and tuberculous (TB) lymphadenitis (33% and 21%, respectively). Sensitivity and negative predictive value for TB were 97% and 93%, respectively. The next most common masses were malignant neoplasms, cysts, benign neoplasms and sialadenitis, in 13%, 11%, 9% and 5%, respectively. Carcinomas metastatic to the lymph node were the most common type of cancer, followed by lymphoma and salivary gland carcinoma. The primary site of metastatic carcinomas were nasopharynx (44%) and thyroid (22%). The sensitivity and negative predictive values for the diagnosis of cancer were 95% and 96%, respectively, but reached 100% when lymphoma was excluded. The introduction of FNA reduced the number of lymph node biopsies performed in this hospital by 90%. CONCLUSION: FNA of head and neck masses proved to be a very useful diagnostic tool in separating inflammatory lesions (no surgical excision required) from cystic and neoplastic lesions. It enhanced surgical planning for malignant diseases, allowing rapid referral of lymphomas and cancer cases to tertiary care centers for management. FNA is simple, cost effective and suitable for developing countries and small, secondary care hospitals with limited resources. Skilled personnel and routine audits are the keys to success.     

Diagnostic pitfalls in the fine needle aspiration of thyroid nodules. A study of 555 cases in Chinese patients

The diagnostic value and limitations of fine needle aspiration (FNA) were determined by examining 555 palpable thyroid nodules in Chinese patients who had a definitive diagnosis established by thyroidectomy (529 cases) or large-needle biopsy (26 cases). Of the aspirates, 97.8% were satisfactory for cytologic examination. The overall malignancy rate was 20%. FNA detected 73 (74.5%) of 98 primary malignant tumors and 9 (90%) of 10 metastatic tumors. Diagnostic errors were most commonly due to inadequate specimens and cystic lesions. Cystic fluid, present in one-third of all lesions, was associated with a malignant nodule in 13% of the cases. FNA was most valuable for detecting papillary carcinomas; it may at times suggest the likelihood of a follicular carcinoma.     

Computerized morphometric study on fine needle aspirates of cellular follicular lesions of the thyroid

OBJECTIVE: To investigate the value of computerized nuclear morphometry in the differential diagnosis of cellular follicular lesions of the thyroid cytologically diagnosed on fine needle aspiration (FNA) smears. STUDY DESIGN: Sixty cases of FNA thyroid smears were cytologically diagnosed and classified as follows: 30 cases of follicular carcinoma, 20 cases of cellular hyperplastic nodules and 10 cases of follicular adenoma. Using an image analysis system, two morphometric variables, nuclear area and major axis length of the nucleus, were measured for each case. RESULTS: For both nuclear morphometric variables, statistical differences were found between carcinomas and hyperplastic nodules as well as between carcinomas and adenomas. No statistical differences were found between the nuclear variables in either hyperplastic nodules or adenomas. CONCLUSION: The results confirm the aim of our study, to establish nuclear morphometry by computerized image analysis as an additional tool in the differential diagnosis of thyroid follicular lesions cytologically diagnosed on FNA smears.     

Fine needle aspiration cytologic study of the solitary thyroid nodule. Profile of 308 cases with histologic correlation

The cytologic features and diagnoses of 308 solitary thyroid nodules subjected to fine needle aspiration (FNA) are presented and correlated with the histopathology. The findings reconfirmed the overall utility of FNA cytology in the differentiation of benign from neoplastic lesions and in the specific diagnosis of most types of thyroid lesions. The difficulty in the diagnosis of follicular carcinoma and in its differentiation from follicular adenoma is highlighted. Of note was the finding of Hürthle-cell populations in several types of lesions, which represents a potential diagnostic problem; this potential difficulty was lessened by sampling two or three areas within a nodule, thus obtaining a more truly representative specimen.     

The utility of assessing the gross appearances of FNA specimens

F. Mayall, A. Cormack, S. Slater and K. McAnulty The utility of assessing the gross appearances of FNA specimens Objective: Ideally, fine needle aspiration (FNA) cytology should be performed with near‐patient assessment of the adequacy of the specimen by a cytopathologist. However, this is often not feasible. A cruder alternative is for the FNA practitioner to examine the gross appearances of the specimen and to try to predict the its quality. This study set out to determine the value of this approach. Methods: The study was conducted in tertiary public hospitals in New Zealand and the UK. FNA gross material grading was performed by a variety of pathologists on FNA samples taken using manual guidance and image guidance. The FNA gross material grade was compared with the findings on microscopic examination. Results: Nine out of 123 FNA samples were assessed as Grade 1 (unlikely to contain diagnostic material). All were subsequently reported as having insufficient diagnostic tissue on microscopic examination. Forty‐two of the FNA samples were assessed as Grade 2 (possibly contains diagnostic material) and 46 as Grade 3 (probably contains diagnostic material). None from either of these grades was reported as showing insufficient diagnostic material on microscopic examination. Twenty‐six cases were reported as Grade 4 (material suggesting a specific diagnosis). None of these was reported as showing insufficient diagnostic material on microscopic examination. The most common Grade 4 provisional diagnosis was that of a colloid cyst or colloid nodule of the thyroid (seven cases). Only two cases had misleading Grade 4 provisional diagnoses. Both were thought to be pus on gross examination but showed necrotic carcinoma on microscopic examination. Conclusions: The gross appearances of FNA samples can usually predict the adequacy of the samples and sometimes predict the final microscopic diagnosis. However, near‐patient microscopic assessment of FNA specimens is preferable if available.     

Clinicopathologic management of tumors of the thyroid gland in an endemic goiter area. Combined use of preoperative fine needle aspiration biopsy and intraoperative frozen section

In total, 15,325 fine needle aspiration (FNA) biopsies of the thyroid were examined in the Department of Pathology of the University of Innsbruck, Austria, between 1976 and 1985, with the cytologic results histologically verified in 3,112 cases. Since (1) it is frequently impossible to distinguish benign from malignant encapsulated follicular thyroid tumors by cytologic criteria and (2) there is a high level of follicular thyroid carcinoma in our endemic goiter area, we have adopted a diagnostic strategy that accepts a high percentage of false-positive cytologic results in order not to miss highly differentiated follicular carcinoma. To avoid unnecessarily extensive surgical treatment, 1,079 intraoperative frozen section examinations of the thyroid were performed in the same time period in (1) patients with preoperative suspicious or positive FNA cytologic findings, (2) cases with suspicious clinical and anamnestic data and (3) tumors with a suspicious macroscopic appearance without preoperative FNA or with negative or unsatisfactory cytologic findings. In 48 cases (4.5%), the frozen section diagnosis had to be revised after examination of paraffin-embedded tissue. An intraoperative false-positive diagnosis was obtained in 3 cases (0.3%) while a false-negative diagnosis was made in 45 cases (4.2%). The main effort in examining frozen sections should be concentrated on avoiding false-positive errors, which can lead to unnecessary thyroidectomies.     

Fine needle aspiration cytology of thyroid gland diseases

From 1982 to 1987, 2,433 lesions of the thyroid gland in 1,796 patients were examined by fine needle aspiration (FNA). Cytopathology classified 66.91% of the aspirates as benign, 10.76% as thyroiditis, 4.89% as suspected (unspecified) neoplasia, 1.31% as positive for malignancy and 16.11% (392) as unsatisfactory. The histologic diagnoses in 257 cases were compared with cytologic diagnoses to determine the accuracy of FNA cytology of thyroid lesions, yielding a sensitivity of 71.43%, a specificity of 100% and an accuracy of 95.09%. This data strongly supports thyroid FNA as an important preoperative diagnostic tool. Follicular carcinomas were difficult to cytologically differentiate from nonmalignant follicular neoplasms, and papillary thyroid carcinomas less than 2 cm in diameter in elderly patients were frequently misdiagnosed or diagnosed only as "suspect lesion."     

The impact of the non‐invasive follicular thyroid neoplasm with papillary‐like nuclear feature terminology in the routine diagnosis of thyroid tumours

Background

Due to the recent proposal of the non‐invasive follicular thyroid neoplasm with papillary‐like nuclear feature (NIFTP) category, the authors analyse the state of the art in the challenging diagnosis of follicular thyroid neoplasms in routine practice.

Methods and results

A consecutive series of 200 histological diagnoses, with complete cytological correlation, was analysed following the introduction of the NIFTP definition. The study was conducted in a general hospital with a high prevalence of thyroid benign nodules that accounted for approximately 60% of surgically‐treated nodules. The significant incidence of the new NIFTP category was 7%. Concurrently, a gradual decrease of the follicular variant of papillary thyroid carcinoma (fvPTC) was observed (3.5%). When evaluating the FNA biopsies within the NIFTP group, despite the systematic evaluation of nuclear crowding, enlargement, irregularities and clearing, the final cytological class was often indeterminate for malignancy (Thy3/III‐IV, 71%). At histology, the application of the semiquantitative NIFTP score for the evaluation of the PTC‐like nuclear features was able to discriminate benign lesions (score 0/1) from fvPTC (score 2/3). A certain degree of overlapping still persisted between NIFTP and fvPTC (score 2) or between NIFTP and benign lesions (score 1).

Conclusions

In the routine evaluation of FNA biopsies, the presence of subtle and questionable PTC‐like nuclear features still remains a controversial aspect of the diagnostic workflow. Given that the NIFTP category was introduced to stratify the low‐risk group of thyroid tumours more precisely, pathologists should force themselves to apply the nuclear score rigorously and to classify cases assigned a score of 1 as benign proliferations.

     

Histopathological diagnosis of thyroid cancer in a multicenter trial

INTRODUCTION: In the front of the problems related to the differentiation between benign and malignant thyroid tumors we decided to perform a multicentre study in order to validate diagnoses of malignant thyroid tumors and assess the inter-observer variability. MATERIAL AND METHODS: Material included 690 cases of malignant and benign thyroid lesions with primary histopathology established in 1985-1999. These cases were selected to multicentre study. The studies were sent from centres which agreed to participate in the project and than coded in the independent centre--Department of Nuclear Medicine and Endocrine Oncology. 40 pathologists from 25 centres provided their diagnoses which were compared with the reference ones. RESULTS: 10 547 diagnoses were evaluated, both on their accuracy of the distinction between malignant and benign lesions and on their accuracy of cancer histotype definition. The reference diagnosis was made by an agreement between four expert pathologists (D.L., S.S., J.S. and A.K.). The participants diagnosed 21% of cases differently than experts. Concerning the diagnosis of cancer histotype, the difference between participants diagnosis and the reference one was even higher. The best concordance was achieved in the diagnosis of papillary thyroid cancer, however, on the cost of cancer overdiagnosis by some participants. Follicular cancer was diagnosed accurately only in 75.4% of cases. CONCLUSION: The study documents a high inter-observer variability of thyroid cancer diagnosis and confirms the lesser accuracy of diagnosis of follicular cancer.     

Evaluation of HMFG2 and thyroglobulin in the diagnosis of thyroid fine needle aspiration (FNA)

In order to appraise the usefulness of HMFG₂ and thyroglobulin (Tg) as specific markers for the diagnosis of thyroid disease, we studied 63 FNA smears. Cases tested included 30 benign (nine colloid goitres, six cases of Hashimoto's thyroiditis, six Hürthle cell adenomas, nine follicular adenomas) and 33 malignant lesions (nine follicular carcinomas, 12 papillary carcinomas, nine anaplastic carcinomas, three medullary carcinomas). All cases with malignant lesions except the anaplastic carcinomas were positive for HMFG₂. Immunoreactive cells to HMFG₂ were also found in 15 adenomas out of 30 benign cases. Positive Tg reaction was found in benign and malignant thyroid lesions, except six cases of Hashimoto's thyroiditis, nine anaplastic and three medullary carcinomas. The results obtained indicate that morphology paired with immunocytochemistry can usually depict a more specific profile of thyroid lesions for better evaluation of the pathology.     

Potential diagnostic markers in nodular lesions of the thyroid gland: an immunohistochemical study

Aims: The differential diagnosis of thyroid nodules in routine practice can be problemmatic for both pathologists and clinicians. Effective treatment requires a determination of the biological nature of the lesions. For this reason, ancilliary diagnostic markers along with histological examination of the nodules may be useful. The objective of this study was to evaluate the diagnostic usefulness of novel markers in the diagnosis of hyperplastic and neoplastic nodules. Methods: Forty eight thyroid lesions forming four diagnostic groups including adenomatous goiters (AS), follicular adenomas (FA), follicular (FC) and papillary carcinomas (PC) were examined using standard immunohistochemical methods. Monoclonal antibodies against galectin-3, matrix metalloproteinases (MMPs) -2 and -7 and endothelial markers CD31 and CD105 were used. Results: The cytoplasmatic expression of galectin-3 was positive in all cases of papillary carcinoma. Moreover, statistically significant differences between fused groups of benign (AS and FA) and malignant lesions (FC and PC) were found Fischer's exact test (p = 0.0001). No significant differences in cytoplasmic expression of MMPs -2 and -7 and in vascular density assessed by using of both endothelial markers between benign lesions and malignant tumors were revealed. Conclusions: Galectin-3 appears to be a useful marker in the diagnosis of papillary carcinoma only. The matrix metalloproteinases-2 and -7 are not helpful in distinguishing hyperplastic and neoplastic thyroid nodules. Endothelial markers do not appear to be suitable for thyroid differential diagnosis. A panel of antibodies in the differential diagnosis of thyroid nodular lesions would seem most suitable and further studies with larger sets of patients are awaited.     

Distinction between colloid nodules and follicular neoplasms of the thyroid. Further observations on cell blocks

The differentiation between colloid nodules and follicular neoplasms may be difficult in lesions yielding only microfollicles by fine needle aspiration (FNA). In a retrospective study of 35 follicular lesions, the FNA smears and cell blocks and the excised specimens were reviewed for possible distinguishing features. Columnar cells lining follicles and prominent sinusoidal stroma were seen only in follicular neoplasms; these were more easily appreciated in the cell blocks. Nuclear features and fibrosis were not helpful because they were found in both groups of lesions. Attention to the nuclear morphology was important, however, for the diagnosis of the follicular variant of papillary carcinoma. A repeat FNA might be helpful in obtaining hyperplastic papillae and fragments of dilated follicles for a diagnosis of colloid nodule in half of the cases. A few lesions with predominant microfollicular patterns were even problematic to diagnose on the excised specimens.     

Learning vector quantizer in the investigation of thyroid lesions

OBJECTIVE: To investigate the capability of the learning vector quantizer (LVQ) in the discrimination of benign from malignant thyroid lesions. STUDY DESIGN: The study was performed on May-Grünwald-Giemsa-stained smears taken by fine needle aspiration (FNA). Using a custom image analysis system, 25 features that describe the size, shape and texture of approximately 100 nuclei were measured from each case. Statistical features were extracted from each case, and a linear regression analysis was performed to detect the statistically significant features. The cases were distributed by category, as follows: 100 cases of goiter and follicular adenomas, 11 cases of follicular carcinoma, 35 cases of papillary carcinoma, 24 cases of oncocytic adenoma, 8 cases of oncocytic carcinoma and 20 cases of Hashimoto thyroiditis. About 30% of the cases from each class were used for training two LVQ classifiers. The remaining 139 cases, out of a total of 198, were used as the test set. A classifier was used to discriminate into four classes and a second into two classes. RESULTS: The application of LVQ neural networks allows good discrimination between benign and malignant lesions (O.A. = 97.8). However, reliable discrimination of the cytologic types of the lesions was not obtained. CONCLUSION: These results indicate that the use of neural networks combined with image morphometry may offer useful information on the potential for malignancy of thyroid lesions and may improve the diagnostic accuracy of FNA of the thyroid gland, especially in cases of follicular neoplasms classified as suspicious for malignancy and in cases of oncocytic tumors.     

Fine needle aspiration cytology in the diagnosis of bone lesions

OBJECTIVE: Fine needle aspiration cytology (FNAC) in combination with radiological examination has recently gained clinical recognition for evaluating skeletal lesions. We evaluated our experience with the use of FNA in diagnosing bone lesions with emphasis on areas of difficulty and limitations. MATERIALS AND METHODS: Over a period of 5 years FNA was performed in 66 cases of bone lesions. Aspirations were done by cytopathologists using 22-gauge needle. Out of 66 cases unsatisfactory aspirate was obtained in 12 cases. Cytohistological correlation was available in 19 cases. RESULTS: Adequate aspirates were categorized into neoplastic (27 cases) and non-neoplastic (27 cases) lesions. Of the 27 neoplastic aspirates, 20 were malignant (12 primary, 8 metastatic deposits) and 7 were benign. In the malignant group osteosarcoma was correctly diagnosed in 3 cases while other 3 were labeled as sarcoma NOS because of lack of osteoid. Metastatic deposits were sub-typed in 6 cases; from renal cell carcinoma (3 cases), proststic adenocarcinoma, follicular carcinoma thyroid, and squamous cell carcinoma. Neoplastic group comprised of 6 cases of cysts and 21 cases of chronic osteomyelitis. Thirteen cases were diagnosed as tuberculous osteomyelitis. CONCLUSIONS: FNA is a frequent indication in metastases in the bone where distinct cytologic features can even identify an unknown primary. However, diagnosis of primary tumours of the bone is limited by precise subtyping of the tumours. FNA has emerged as a cost effective tool for initial diagnosis of both neoplastic and non-neoplastic lesions of the bone.     

Posters. P13 Cytohistological correlation in 212 FNAs of thyroid: analysis of discordant cases

Aim To detect major pitafalls in thyroid FNA and to confirm its in a clinical sensitivity and specificity. Methods A total of 9251 fine needle aspirations biopsy carried out at Bellaria Hospital in Bologna from 1991 to 2000 by a pathologist in the FNA Clinic or by a clinician under ultrasonic guidance using a small needle (25–27 G); at least two passes have been made for each nodule. The specimen was considered satisfactory if at least five groups of follicular cells with at least 10 cells each, were seen. The cytological results were tiered in a four categories classification: inadequate, negative, suspicious and positive. Cyto‐histological correlations were available in 212 cases: 127 benign lesions and 85 malignant lesions. An analysis of false positive cases and false negative cases was performed and discordant case reviewed according to the flowing criteria: architecture, cellularity, colloid, pseudoinclusions, nuclear groovings, chromatin pattern, nuclear membrane, cytoplasm, naked nuclei and lymphocytes. Results Diagnostic distribution in 9251 FNAs from the thyroid: 88.6% negatives, 2.8 suspicious, 2.4% positives and 6.2% inadequates. Specificity was 85.8% and sensitivity was 78.8%. Among the 18 false negative cases eight were papillary microcarcinomas, four papillary carcinomas, five follicular carcinoma and one a Hurtle cell carcinoma. Four false positive cases were found: three reported as papillary carcinomas and one as carcinoma NOS. Review of false positives showed that in three cases the colloid was fluid, in three cases nuclear grooving was rare or absent, in two cases degenerative vacuoles at MGG were interpreted as nuclear inclusions and in three cases benign naked nuclei were present in the background. Review of false negatives confirmed lack of malignant features in 13 (eight papillary microcarcinomas and five follicular carcinomas), five were interpretation errors (three papillary carcinomas, one follicular, one Hurtle cell). Conclusion FNAC of the thyroid is a sensitive and specific method of assessment for thyroid nodules but false negative and false positive cases do occur. Use of all and only few criteria enhances diagnostic accuracy.     

The bethesda terminology for reporting thyroid cytopathology: from theory to practice in europe

Objectives: A 2007 conference held at the National Cancer Institute, Bethesda, Md., USA, proposed a new terminology for classifying the results of thyroid fine-needle aspiration (FNA) - The Bethesda System for Reporting Thyroid Cytology (TBSRTC). The need to standardize thyroid FNA terminology was emphasized during the 35th European Congress of Cytology in 2009. An interobserver review study to assess the new terminology for analyzing the results of thyroid FNA was organized by the scientific committee of the European Federation of Cytology Societies. Study Design: Four experts in thyroid FNA examined and classified 116 FNAs according to the 6 levels of TBSRTC which are: nondiagnostic (ND); benign; atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS); follicular neoplasm/suspicious for a follicular neoplasm (FN/SFN), with those of Hürthle cell type reported as follicular neoplasm, Hürthle cell type/suspicious for a follicular neoplasm, Hürthle cell type (FNHCT/SFNHCT); suspicious (SUS), and malignant. Results: The total consensus was 62.1%; the cytopathologists disagreed on 44 cases, including 8 cases of AUS/FLUS and 18 of FN/SFN; 59% of the cases had no consensus. They agreed on 73 and 80% of the cases classified as benign and malignant, respectively, and on 58.3% of the SUS cases. The percentage of no consensus for each expert was between 32 and 39%. Conclusions: Disagreement regarding the use of TBSRTC terminology for classifying the results of thyroid FNA mainly occurred in the most-often criticized categories of AUS/FLUS and FN/SFN.