Posters. P17 Accuracy of fine needle aspiration cytology in diagnosis of thyroid swellings

Introduction Fine needle aspiration cytology is regarded as the gold standard investigation in diagnosis of thyroid swellings. Published data suggest an overall accuracy rate of 75% 1 in the detection of thyroid malignancy. The aim of this study was to determine the accuracy of FNA cytology in detection of thyroid malignancy in our surgical unit. Methods Between 1989–2002, 144 patients who underwent thyroid resection by single consultant surgeon and who had pre‐operative FNA were enrolled in this retrospective study. The pre‐operative FNA results were compared with definitive histological diagnosis following thyroid resection. Fine needle aspiration cytology was performed using aspirate and non‐aspirate techniques on each thyroid swelling. The cytological sample was assessed by a single cytopathologist and was classified as inadequate, non‐neoplastic, neoplastic, suspicious or indeterminate. The histology was classified as non‐neoplastic (benign) and neoplastic (malignant). Results Fine needle aspiration cytology analysis revealed 94 (13.88%) non‐neoplastic, six (65.27%) neoplastic and 20 (4.16%) suspicious aspirates. Twenty (13.88%) samples were inadequate and four (2.77%) samples were indeterminate. Histological analysis showed 118 (81.94%) benign, 26 (18.05%) malignant specimens. Fine needle aspiration cytology had a sensitivity, specificity and accuracy rate of 52.6%, 86.6% and 79.1%, respectively for diagnosing thyroid malignancy. Conclusion The results are comparable with the current published data and demonstrate that FNA cytology in our hands is accurate investigation for pre‐operative diagnosis for the detection of thyroid malignancy.     

Fine needle aspiration of the hot thyroid nodule

The use of fine needle aspiration (FNA) cytology in the evaluation of solitary hot thyroid nodules was examined in 24 patients. Satisfactory FNA specimens were obtained from 22 patients. None of the cytologic samples was considered malignant or suspicious for malignancy. The cytologic findings were indeterminate in one instance--a smear with follicular features. The smears from the other 21 patients were judged to be benign. If FNA had been used as the initial diagnostic step, the need for a thyroid scan would thus perhaps have been avoided in 21 of the 24 patients. These results support the idea that FNA is the most effective procedure in the evaluation of the solitary thyroid nodule, whether functional or not.     

Use of immunohistochemistry in fine needle aspiration of thyroid nodules in patients with a history of malignancy. A report of two cases

BACKGROUND: A history of a nonthyroid malignancy may present a diagnostic dilemma in the assessment of fine needle aspiration (FNA) of thyroid nodules. One reported series, on patients with prior malignancies and a thyroid nodule, indicated that in 17% of patients, the thyroid nodule represented metastatic malignancy, 6% were classified as primary thyroid cancers, and the remainder were benign or inconclusive lesions. The resolution of this problem is essential to patient management. CASES: We report two cases in which patients with a history of renal cell carcinoma presented with a thyroid nodule. The first patient was an 80-year-old female whose Papanicolaou-stained FNA demonstrated clusters of round to polygonal cells with round to ovoid, hyperchromatic nuclei and abundant, wispy cytoplasm. The second patient was a 55-year-old female with clusters and single cells with round to oval, eccentric nuclei and copious, granular, gray cytoplasm noted on Papanicolaou-stained material. In each case, the diagnosis was inconclusive on initial review of Papanicolaou-stained slides, and immunohistochemical staining was ordered to better characterize the lesions. Tumor cells from case 1 were positive for cytokeratin cocktail and vimentin and negative for thyroglobulin, epithelial membrane antigen and calcitonin, suggestive of metastatic renal cell carcinoma. In contrast, the tumor cells from case 2 expressed cytokeratin, thyroglobulin and vimentin, consistent with a primary thyroid neoplasm. In each case, the cytologic diagnoses were confirmed in the resected specimens. CONCLUSION: Immunohistochemistry is a helpful adjunct in the evaluation of thyroid nodules in patients with a past history of malignancy.     

Fine needle aspiration cytology of the thyroid: a comparison of 5469 cytological and final histological diagnoses

OBJECTIVE: We evaluated the efficacy of fine needle aspiration cytology (FNAC) of the thyroid in a series of 5469 lesions with histological control and studied the causes of, and the possibility of reducing the limitations of the method. METHODS: FNAC was always performed by a pathologist under the guidance of a clinician, using a 22-gauge needle. Generally two aspirations were carried out, and usually four slides were obtained for each nodule; they were then stained with May-Grünwald-Giemsa and with Papanicolaou. The cytological diagnoses were classified in four groups: inadequate, benign, suspicious and malignant. RESULTS: We obtained a complete sensitivity of 93.4%, a positive predictive value of malignancy of 98.6%, and a specificity of 74.9%. At histological control, the cytological diagnosis of Hurthle cell neoplasm corresponded to a significantly higher incidence of malignant neoplasms than the diagnosis of non-Hurthle cell follicular neoplasm (32.1% versus 15.5%). There were 66 false-negative findings, the main cause of diagnostic error (24 cases) being failure to recognize the follicular variant of papillary carcinoma. The number of inadequate FNACs was low (4.2%). CONCLUSION: Our study confirmed the great efficacy of thyroid FNAC. A cytological diagnosis of Hurthle cell neoplasm should be considered an indicator of high risk. Awareness that failure to recognize the follicular variant of papillary carcinoma was the main problem in the interpretation of thyroid FNAC should lead to a decrease of false-negative diagnoses. The inadequate rate was very low, as it was the pathologist personally who performed the needle aspiration.     

Malignancy Risk Analysis in Patients with Inadequate Fine Needle Aspiration Cytology (FNAC) of the Thyroid

Background

Thyroid fine needle aspiration cytology (FNAC) is the standard diagnostic modality for thyroid nodules. However, it has limitations among which is the incidence of non-diagnostic results (Thy1). Management of cases with repeatedly non-diagnostic FNAC ranges from simple observation to surgical intervention. We aim to evaluate the incidence of malignancy in non-diagnostic FNAC, and the success rate of repeated FNAC. We also aim to evaluate risk factors for malignancy in patients with non-diagnostic FNAC.

Materials and Methods

Retrospective analyses of consecutive cases with thyroid non diagnostic FNAC results were included.

Results

Out of total 1657 thyroid FNAC done during the study period, there were 264 (15.9%) non-diagnostic FNAC on the first attempt. On repeating those, the rate of a non-diagnostic result on second FNAC was 61.8% and on third FNAC was 47.2%. The overall malignancy rate in Thy1 FNAC was 4.5% (42% papillary, 42% follicular and 8% anaplastic), and the yield of malignancy decreased considerably with successive non-diagnostic FNAC. Ultrasound guidance by an experienced head neck radiologist produced the lowest non-diagnostic rate (38%) on repetition compared to US guidance by a generalist radiologist (65%) and by non US guidance (90%).

Conclusions

There is a low risk of malignancy in patients with a non-diagnostic FNAC result, commensurate to the risk of any nodule. The yield of malignancy decreased considerably with successive non-diagnostic FNAC.     

Papillary carcinoma of the thyroid occurring during pregnancy. Report of a case diagnosed by fine needle aspiration cytology

A case of papillary carcinoma of the thyroid gland occurring during pregnancy in a 29-year-old woman is described. The enlarged thyroid nodule was first detected at 10 weeks of gestation; fine needle aspiration (FNA) of the nodule showed no cytologic evidence of malignancy. Repeat FNA at 30 weeks of gestation produced inadequate material for diagnosis. A final FNA at 38 weeks of gestation showed classic cytologic features of papillary carcinoma, including papillary structures, grooved nuclei and intranuclear cytoplasmic inclusions. After delivery, the patient was treated with total thyroidectomy and cervical lymph node dissection. The enlargement of the nodule in this case during the course of the pregnancy suggests a relationship between pregnancy and the malignant development of thyroid nodules; this is discussed along with the utility of FNA cytology for diagnosing thyroid cancers during pregnancy.     

Importance of FNAC in the detection of tumours within multinodular goitre of the thyroid

The primary challenge in the management of a multinodular thyroid gland is to rule out malignancy. The present study was undertaken to assess the value of preoperative ultrasound-guided fine needle aspiration cytology (FNAC) in diagnosing tumours of the thyroid gland. Of the 80 patients operated for multinodular lesions, malignant tumours were found in 29 and benign tumours in 36 patients (81%) and non-tumorous lesions in 15 (19%) patients. Compared with the histopathological postoperative diagnosis, the overall sensitivity of FNAC was 85% and specificity 88%. Current morphological diagnosis of the nodules in multinodular goitre requires thorough preoperative examination, including ultrasound-guided FNAC in order to establish the appropriate management.     

Assessing The Risk of False-Negative Fine-Needle Aspiration Cytology and of Incidental Cancer in Nodular Goiter

ObjectiveIn cases of multinodular goiter with negative cytologic result, reasonable management options include surgical treatment, simple follow-up, or more recently introduced conservative therapies such as laser or radiofrequency ablation, and recombinant human thyroid-stimulating hormone-augmented radioiodine. For patients who are eligible for follow-up or nonsurgical treatments, the possibility that they may have an undiagnosed malignancy (false-negative [FN]-fine-needle aspiration cytology [FNAC] result or incidental thyroid cancer [ITC]) should be considered. The aim of our study was to assess the risk of malignancy in patients known to have presumably benign thyroid disease.MethodsSurgical series of patients who underwent total thyroidectomy for benign disease between 2000 and 2010 at two Italian centers were reviewed. Patients with any preoperative suspicion of malignancy were excluded.ResultsHistologic examination revealed that 84 of 970 (8.6%) thyroidectomized patients had malignancy (5% ITC and 3.6% FN-FNAC), with 89.8% of ITCs having a diameter <10 mm, and 65.7% of FN-FNAC cancers having a diameter >30 mm. Sixty-seven thyroid malignancy patients (79.8%) had stage I disease (American Joint Committee on Cancer criteria). The risk of FN-FNAC increases with increasing size of the nodule, while the risk of ITC increases as nodule size decreases.ResultsThe risk of malignancy in presumably benign thyroid disease cannot be overlooked, but can be minimized through skillfully performed ultrasonography (US) examination and FNAC. Once a patient with multinodular goiter is referred for follow-up or nonsurgical therapy, careful US surveillance is mandatory. (Endocr Pract. 2013;19:444-450)     

Is a five‐category reporting scheme for thyroid fine needle aspiration cytology accurate? Experience of over 18 000 FNAs reported at the same institution during 1998–2007

S. Piana, A. Frasoldati, M. Ferrari, R. Valcavi, E. Froio, V. Barbieri, C. Pedroni and G. Gardini Is a five‐category reporting scheme for thyroid fine needle aspiration cytology accurate? Experience of over 18 000 FNAs reported at the same institution during 1998–2007 Objective: Fine needle aspiration (FNA) has long been recognized as an essential technique for the evaluation of thyroid nodules. Although specific cytological patterns have been recognized, a wide variety of reporting schemes for thyroid FNA results have been adopted. This study reports our experience with a five‐category reporting scheme developed in‐house based on a numeric score and applied to a large series of consecutive thyroid FNAs. It focuses mainly on the accuracy of thyroid FNA as a preoperative test in a large subset of histologically distinct thyroid lesions. Methods: During the 1998–2007 period, 18 359 thyroid ultrasound‐guided FNAs were performed on 15 269 patients; FNA reports were classified according to a C1–C5 reporting scheme: non‐diagnostic (C1), benign (C2), indeterminate (C3), suspicious (C4), and malignant (C5). Results: Non‐diagnostic (C1) and indeterminate (C3) FNA results totalled 2 230 (12.1%) and 1 461 (7.9%), respectively, while suspicious (C4) and malignant (C5) results totalled 238 (1.3%) and 531 (2.9%), respectively. Histological results were available in 2 047 patients, with thyroid malignancy detected in 840. Positive predictive value of FNA was 98.1% with a 49.0 likelihood ratio (LR) of malignancy in patients with a C4/C5 FNA report. Conclusions: This five‐category scheme for thyroid FNA is accurate in discriminating between the virtual certainty of malignancy associated with C5, a high rate (92%) of malignancy associated with C4, and a 98% probability of a histological benign diagnosis associated with C2. Further sub‐classifications of C3 may improve the accuracy of the diagnostic scheme and may help in recognizing patients eligible for a ‘wait and see’ management.     

Fine needle aspiration biopsy in the diagnosis of thyroid nodules

The fine needle aspiration (FNA) biopsies performed on thyroid nodules at Turku University Central Hospital from 1983 to 1988 were reviewed. Of the 1,054 total aspirated nodules, 194 were investigated histologically after thyroid surgery (191 cases) or at autopsy (3 cases). Two cases with an insufficient FNA sample, 4 with an incidental occult papillary carcinoma and 2 cases with carcinoma outside the nodule investigated by FNA biopsy were excluded from the series, leaving 186 histologically confirmed nodules in the final analysis. Three (3%) of the 107 cases with an FNA biopsy diagnosis of benign, 4 (8%) of the 52 with an FNA diagnosis of equivocal, 3 (20%) of the 15 with an FNA diagnosis of suspicious and all 12 (100%) with an FNA diagnosis of malignant were histologically malignant. If only an unequivocally malignant cytologic finding is considered positive, FNA biopsy had a diagnostic specificity of 100%, a sensitivity of 55% and an accuracy of 95% among the histologically confirmed cases. Follow-up revealed no cases of cancer among the 863 thyroids that were not explored surgically. It is concluded that FNA biopsy is a practical method with considerable diagnostic value in the evaluation of thyroid nodules.     

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."     

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.     

Secondary infection and ischemic necrosis after fine needle aspiration for a painful papillary thyroid carcinoma: a case report

BACKGROUND: Papillary thyroid carcinoma (PTC) is often asymptomatic and rarely presents as a painful goiter. Further, the thyroid gland is not easily infected. Therefore, acute suppurative thyroiditis (AST) is unusual. PTC is also seldom combined with AST. We report a case of painful PTC with secondary infection after fine needle aspiration (FNA). CASE: A 19-year-old girl complained of a painful goiter without skin change after an episode of upper airway infection. PTC was diagnosed according to the FNA cytology (FNAC) at another hospital. The goiter became more painful after FNA. The patient's second FNAC at our hospital revealed only many polymorphonuclear leukocytes (PMNs). Antibiotic treatment ameliorated the pain, but the goiter persisted. The third FNAC revealed some PMNs and papillary carcinomatous cells. After total thyroidectomy, pathology revealed ischemic necrosis with a focal PMN aggregation around the needle track and papillary carcinomatous cells nearby. According to the time sequence, secondary infection after FNA was suspected. CONCLUSION: A painful goiter is an unusual presentation of PTC. Although FNAC is feasible for studying a thyroid lesion, malignant cells might be missed when secoandary injection and ischemic necrosis occur after FNA. Therefore, aseptic procedures are necessary to prevent bacteria from seeding into the thyroid.     

Primary squamous cell carcinoma of the thyroid diagnosed by fine needle aspiration cytology. A report of two cases.

BACKGROUND: Primary squamous cell carcinoma of the thyroid is a rare malignant tumor that needs to be distinguished from other neoplasms. CASES: Two males aged 65 and 68 years presented with an enlarged right lobe of the thyroid. Thyroid scintigraphy revealed a cold nodule. Clinically malignancy was suspected. Fine needle aspiration (FNA) revealed numerous clusters and isolated malignant cells, dyskeratotic cells and deposits of eosinophilic granular keratin material. Subtotal thyroidectomy was performed. Histologic findings confirmed the cytologic diagnosis of squamous cell carcinoma. CONCLUSION: Primary squamous cell carcinoma of the thyroid is a rare tumor. FNA findings of this tumor were not reported before. FNA study cannot help to differentiate primary from metastatic squamous cell carcinoma of the thyroid.     

Value of repeated fine needle aspiration cytology in patients with nodular goiter

OBJECTIVE: To assess the value of reaspiration cytology in benign nodular thyroid disease. DESIGN: We prospectively studied 400 patients (365 women, 35 men) aged 46 years (18-89) with nodular thyroid disease and initial benign fine needle aspiration cytology (FNAC). Reaspiration of the same nodule was performed in a median follow-up time of 14 months (6-18). RESULTS: Repeat FNAC was benign in 346 patients (86.5%), insufficient for diagnosis in 42 (10.5%), suspicious in 16 (2.5%) and malignant in 2 (0.5%). All diagnostic changes to suspicious malignant cytology took place in patients with solitary nodules. Surgery confirmed thyroid cancer in the 2 patients with malignant cytology, in 5 of 10 patients with suspicious cytology and in none of 39 patients with benign cytology who underwent surgery for other reasons. Clinical changes (size increase or local symptoms) were not related to changes in cytologic diagnosis after a second aspiration, nor with the results of the biopsy. CONCLUSION: Repeat aspiration cytology of thyroid nodules may correct initial false negative results because of cytologic misdiagnosis, occurring in 1.75% of patients, whereas clinical changes did not contribute to diagnosis change. Repeat aspiration cytology is recommended in all patients with nodular goiter.     

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.     

Histologic analysis and comparison of techniques in fine needle aspiration-induced alterations in thyroid

OBJECTIVE: To assess histologic alterations following fine needle aspiration (FNA) of the thyroid and differentiate these from ominous lesions, such as papillary carcinoma thyroid, as well as assess and compare the degree of tissue trauma from the techniques: needle only vs. needle with syringe, size of needle and number of aspirations. STUDY DESIGN: Thyroidectomy specimens of 100 cases with prior FNA biopsy were selected. The changes called "worrisome histologic alteration following fine needle aspiration of the thyroid" (WHAFFT) were studied. Number of FNAs, needle size and technique were tabulated for 73 of 100 cases. RESULTS: Worrisome changes were confined to areas near the needle tract and hence could be differentiated from ominous lesions. Control cases did not show WHAFFT lesions. Non-aspiration FNA cytology (FNAC) technique results in fewer, less frequent WHAFFT changes. The increasing number of FNAs leads to statistically significant increase in infarction, necrosis and vascular changes. A gradation in the WHAFFT changes, directly proportional to the increasing diameter of the needle, was observed. CONCLUSION: The pathologist should be aware of WHAFFT to avoid misinterpretation. The technique of non-aspiration FNAC is significantly less traumatic. An increase in FNAs or size of needle results in more severe WHAFFT changes.     

High CEA levels in a case of resected colorectal cancer: delayed diagnosis of metachronous medullary thyroid cancer

Background

Carcinoembryonic antigen (CEA) is one of the most widely used tumor markers, and its value in the surveillance of post-operative colorectal cancer is well established. Fluorodeoxyglucose-positron emission tomography (FDG-PET) has been clinically used in colorectal cancer imaging including preoperative staging, evaluation of therapeutic response, detection of disease recurrence, and investigation of unexplained rising tumor markers.

Case presentation

We report a case of resected colorectal cancer presented with rising CEA levels in 5 years, and FDG-PET revealed no definitive evidence of recurrence except abnormal focal FDG uptake in the right thyroid lobe. However, fine needle aspiration cytology (FNAC) of the thyroid nodule showed negative for malignancy. Progressively rising CEA levels were noted over the following 5 years, but serial follow-up examinations did not find evidence of recurrence. Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) was performed subsequently and again showed focal FDG uptake in the right thyroid lobe. This time, FNAC revealed positive for malignancy, in favor of medullary thyroid carcinoma (MTC). The patient underwent total thyroidectomy and modified radical neck dissection, and MTC with cervical nodal metastasis (pT3N1) was diagnosed. He had cervical lymph nodes recurrence 2 years later, which was resected.

Conclusions

This case reminded us that FDG-PET/CT may detect occult tumors resulting in CEA elevation other than colorectal cancer. Moreover, FNA has a higher false negative rate in detecting MTC than other forms of thyroid cancer. Repeat FNAC for the initial negative cytology result and measure of serum calcitonin for the early MTC detection could be more helpful to avoid the delay in MTC diagnosis.

     

Fine needle aspiration cytology and immunocytochemistry in tuberculous thyroiditis: a case report

BACKGROUND: Tuberculosis of the thyroid is very rare and does not strike the clinician as a first clinical diagnosis of a thyroid nodule. To our knowledge, only 40 cases of tuberculous thyroiditis diagnosed by fine needle aspiration cytology (FNAC) are described in the English literature. CASE: We report a case of tuberculous thyroiditis in a young woman who presented with a right-side solitary thyroid nodule of short duration (15 days), diagnosed by FNAC and confirmed by positive immunocytochemistry with monoclonal antibody to Mycobacterium tuberculosis complex. Ziehl Neelsen staining for acid-fast bacilli (AFB) was negative. CONCLUSION: FNAC provides a confident preoperative diagnosis of thyroid tuberculosis, obviating the need for unnecessary surgical removal of thyroid nodule. Immunocytochemistry is an important diagnostic adjunct to FNAC in AFB-negative cases.     

Comparison of 5 Thyroid Ultrasound Stratification Systems for Differentiation of Benign and Malignant Nodules and to Avoid Biopsy Using Histology as Reference Standard

ObjectiveWe aimed to compare the thyroid ultrasound risk stratification systems (RSSs) of the American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS), European TI-RADS, Korean TI-RADS, and American Thyroid Association (ATA), American Association of Clinical Endocrinologists, American College of Endocrinology, and Associazione Medici Endocrinologi guidelines to differentiate benign from malignant thyroid nodules and to avoid unnecessary fine needle aspiration (FNA).MethodsThe records of 1143 nodules ≥1 cm that underwent FNA biopsy and thyroidectomy between 2012 and 2020 at our institution were reviewed. Ultrasound categories and FNA recommendation indications of 5 international RSSs were compared with histopathological findings as benign or malignant. The ultrasound categories and recommended FNA indications, the proportion of the avoidable FNA procedures, and false negative rates (FNRs) by different systems were compared with each other.ResultsOf the 1143 nodules, 45% had thyroid malignancy. FNA recommendation and ultrasound risk classification of ATA guidelines had the highest area under curves of 0.619, and 0.715, respectively. ACR TI-RADS, American Association of Clinical Endocrinologists/American College of Endocrinology/Associazione Medici Endocrinologi guidelines, European TI-RADS, ATA guidelines, and Korean TI-RADS would have avoided FNA for 34.7%, 31%, 25.7%, 20%, and 6% of nodules with an FNR of 24%, 28.5%, 22%, 7.2%, and 1.9%, respectively.ConclusionOur findings showed that all RSSs classified the nodules appropriately for malignancy. ATA guidelines had the highest area under curves and a low FNR, whereas ACR TI-RADS would have spared more patients from FNA with a high FNR.