Diagnosis and reporting of follicular-patterned thyroid lesions by fine needle aspiration

Screening adequacy of unstained thyroid fine needle aspiration samples using a deep learning-based classifier

Fine needle aspiration (FNA) biopsy of thyroid nodules is a safe, cost-effective, and accurate diagnostic method for detecting thyroid cancer. However, about 10% of initial FNA biopsy samples from patients are non-diagnostic and require repeated FNA, which delays the diagnosis and appropriate care. On-site evaluation of the FNA sample can be performed to filter out non-diagnostic FNA samples. Unfortunately, it involves a time-consuming staining process, and a cytopathologist has to be present at the time of FNA. To bypass the staining process and expert interpretation of FNA specimens at the clinics, we developed a deep learning-based ensemble model termed FNA-Net that allows in situ screening of adequacy of unstained thyroid FNA samples smeared on a glass slide which can decrease the non-diagnostic rate in thyroid FNA. FNA-Net combines two deep learning models, a patch-based whole slide image classifier and Faster R-CNN, to detect follicular clusters with high precision. Then, FNA-Net classifies sample slides to be non-diagnostic if the total number of detected follicular clusters is less than a predetermined threshold. With bootstrapped sampling, FNA-Net achieved a 0.81 F1 score and 0.84 AUC in the precision-recall curve for detecting the non-diagnostic slides whose follicular clusters are less than six. We expect that FNA-Net can dramatically reduce the diagnostic cost associated with FNA biopsy and improve the quality of patient care.

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.

Causes of misdiagnoses by thyroid fine-needle aspiration cytology (FNAC): our experience and a systematic review

Objective

FNA is a simple, safe, cost-effective and accurate diagnostic tool for the initial screening of patients with thyroid nodules. The aims of this study were to determine the diagnostic utility of FNAC performed in our institution, assess the cytomorphologic features that contribute to diagnostic errors and propose improvement measures.

Methods

A total of 2781 FNACs were included in the study, and 1122 cases were compared with their histological diagnoses. We retrospectively reexamined our discordant (both false-negative and false-positive) cases and performed a systematic review of previous studies on causes of misdiagnoses.

Results

When DC V and DC VI were both considered cytologic-positive, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy were 98.3, 30.9, 94.9, 58.3 and 93.5%, respectively. If DC VI was considered cytologic-positive, the sensitivity, specificity, PPV, NPV and diagnostic accuracy of FNAC were 98.0, 84.0, 99.4, 58.3, and 97.5% respectively. The main cause of false-negative diagnoses was sampling error (13/15, 86.7%), while interpretation error led to the majority of the false-positive diagnoses (38/47, 80.9%). Overlapping cytological features in adenomatous hyperplasia, thyroiditis and cystic lesions were the major factors contributing to interpretation errors, while the size and number of nodules may have led to false-negative diagnoses because of heterogeneity and unsampled areas.

Conclusions

The sensitivity and PPV of thyroid FNAC in our institution were higher than those in the published data, while the specificity and NPV were lower. Regarding the FNA category DC V, a frozen section analysis during diagnostic lobectomy is necessary. Multiple passes should be performed in various parts of a large nodule or from different nodules to reduce the risk of false-negative findings. Cytopathologists should strengthen their criteria for the identification of adenomatous hyperplasia, thyroiditis and cystic lesions to avoid false-positive diagnoses. NIFTP has little effect on diagnostic accuracy and the distribution of diagnostic errors.

Clinical impact of a cytological screening system using cyclin D1 immunostaining and genomic analysis for the diagnosis of thyroid nodules

Background

Fine-needle aspiration (FNA) is the most reliable method for diagnosing thyroid nodules; however, some features such as atypia of undetermined significance or follicular lesion of undetermined significance can confound efforts to identify malignancies. Similar to BRAF, cyclin D1 may be a strong marker of cell proliferation.

Methods

One hundred two patients with thyroidal nodule were enrolled in this prospective study.

Expression of cyclin D1 in thyroid nodules was determined by immunohistochemistry using both surgical specimens and their cytological specimens. The identification of the optimal cut off points for the diagnosis of malignancy were evaluated using the receiver operating characteristic (ROC) curves and the assessment of the area under the ROC curve (AUC). The specificity, sensitivity, positive predictive value (PPV) of markers were evaluated from crosstabs based on cut off points and significance were calculated. We also analyzed genetic variants by target NGS for thyroid nodule samples.

Results

The positive predictive value (PPV) and median stain ratio (MSR) of cyclin D1 nuclear staining was determined in papillary thyroid carcinoma (PPV = 91.5%, MSR = 48.5%), follicular adenoma (PPV = 66.7%, MSR = 13.1%), and adenomatous goiter and inflammation controls (MSR = 3.4%). In FNA samples, a threshold of 46% of immunolabelled cells allows to discriminate malignant lesions from benign ones (P < 0.0001), with 81% sensitivity and 100% specificity. A 46% cutoff value for positive cyclin D1 immunostaining in thyroid cells demonstrated 81% sensitivity and 100% specificity. In surgical specimens, ROC curve analysis showed a 5.8% cyclin D1 immunostaining score predicted thyroid neoplasms at 94.4% sensitivity and 92.3% specificity (P = 0.003), while a 15.7% score predicted malignancy at 86.4% sensitivity and 80.5% specificity (P < 0.0001). Finally, three tested clinico-pathological variables (extra thyroidal extension, intraglandular metastasis, and lymph node metastasis) were significant predictors of cyclin D1 immunostaining (P < 0.001).

Conclusion

Our cytological cyclin D1 screening system provides a simple, accurate, and convenient diagnostic method in precision medicine enabling ready determination of personalized treatment strategies for patients by next generation sequencing using cytological sample.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5452-4) contains supplementary material, which is available to authorized users.

Cytological Features That Differentiate Follicular Neoplasm from Mimicking Lesions

Background

It is difficult to correctly diagnose follicular neoplasms (FNs) on fine-needle aspiration cytology (FNAC) because it shares many cytological features with other mimicking lesions. The aim of this study was to identify the cytological features that differentiate FNs from mimicking lesions.

Methods

We included the cytological slides from 116 cases of thyroid FN diagnosed on FNAC, and included their subsequent histological diagnoses. We evaluated the cytological architectural pattern and nuclear features of the lesions according to their histological groups.

Results

The final histological diagnoses of the 116 cases varied, and included 51 FNs (44%), 47 papillary thyroid carcinomas (40%) including follicular variant, and seventeen cellular nodular hyperplasias (15%). Regardless of the final histological diagnosis, microfollicular pattern was observed in most cases. On the other hand, trabecular pattern was identified in 34% of FNs, but not in any other lesions. Additionally, elongated nuclei and ground glass chromatin were found in only some papillary thyroid carcinomas.

Conclusions

This study shows that the trabecular pattern is a representative cytological feature of FNs that can be used to distinguish FNs from mimicking lesions. In addition, nuclear shape and chromatin pattern can be used to further confirm the diagnosis of FNs from mimicking lesions through FNAC.

Is TSH necessary for initial assessment of thyroid nodules?

OBJECTIVE

The use of thyrotropin (TSH) in the initial assessment of thyroid nodules is inefficient and leads to unnecessary assessment costs. We compared the total costs of thyroid nodule assessment with or without the use of TSH in the initial assessment.

METHODS

A total of 1808 patients with thyroid nodules received TSH, fine-needle aspiration (FNA) and thyroid scintigraphy (TS) assessment, including 83 autonomously functioning thyroid nodule (AFTN) cases and 1725 non-AFTN cases. The total costs of the TSH strategy and non-TSH strategies were compared. The ratio of single-use costs of FNA to TS (C_FNA/TS ) was used as the main outcome measure.

RESULTS

Only when 6·03 ≤ C_FNA/TS ≤ 27·17, the lowest total costs were associated with using the conventional TSH strategy. When C_FNA/TS <6·03 or C_FNA/TS >27·17, the lowest costs were found with FNA and TS, respectively.

CONCLUSION

From the perspective of cost economics, in iodine-sufficient areas, we recommend that the decision on the use of TSH for the initial assessment of thyroid nodules should be based on the testing costs of FNA and TS in that medical unit.

Ultrasonographic Differentiation Between Nodular Hyperplasia and Neoplastic Follicular-Patterned Lesions of the Thyroid Gland

We evaluate the gray-scale ultrasonographic characteristics that differentiate between nodular hyperplasia (NH) and neoplastic follicular-patterned lesions (NFPLs) of the thyroid gland. Ultrasonographic features of 750 patients with 832 thyroid nodules (NH, n = 361; or NFPLs, follicular adenoma, n = 123; follicular carcinoma, n = 159; and follicular variant papillary carcinoma, n = 189) were analyzed. Except for echogenicity, over two-thirds of the cases of NH and NFPLs share the ultrasonographic characteristics of solid internal content, a well-defined smooth margin and round-to-ovoid shape. Independent predictors for NH were non-solid internal content (sensitivity 27.1%, specificity 90.2%), isoechogenicity (sensitivity 69.5%, specificity 63.5%) and an ill-defined margin (sensitivity 18.8%, specificity 94.5%). Independent predictors for NFPLs were hypoechogenicity (sensitivity 60.5%, specificity 70.4%), marked hypoechogenicity (sensitivity 2.8%, specificity 99.4%) and taller-than-wide shape (sensitivity 6.6%, specificity 98.1%). Although NH and NFPLs commonly share ultrasonographic characteristics, non-solid internal content and ill-defined margin are specific to NH and marked hypoechogenicity and taller-than-wide shape are specific to NFPLs.

Evaluating the accuracy of fine needle aspiration and frozen section based on permanent histology in patients with follicular lesions

BACKGROUND

Fine needle aspiration (FNA) has led to a decrease in unnecessary surgeries for thyroid nodules. This study was designed to compare diagnostic value of FNA and frozen section methods in the follicular lesions.

METHODS

This is a cross-sectional study based on the medical records of 42 patients who were referred to surgery clinic of Rasool-e-Akram hospital in Tehran with complaint of thyroid nodules. All FNAs were diagnosed as follicular lesions in pathologic evaluation. All the patients underwent thyroid surgery and their frozen section results were also assessed. Finally, diagnostic value of the two tests was compared based on final permanent histologic report.

RESULTS

Forty two patients with follicular thyroid nodules diagnosed with FNA were included. During the operation, using frozen sections, diagnosis of papillary carcinoma, non-papillary malignancies, benign lesion and intermediate cytology was made in 13 (31%), 3 (7%), 25 (59.5%), 1 (2.5%) patients, respectively. RESULTS of permanent histology showed that follicular adenoma is the most prevalent lesion which appeared in 25 (59.5%) cases. Papillary and follicular carcinomas were detected in 10 (23.8%) and 4 (9.5%) cases, respectively.

CONCLUSION

RESULTS of the study demonstrate a 73% reduction in second surgery in patients with follicular thyroid lesions based on intraoperative frozen section results.

Diagnostic accuracy of fine needle aspiration cytology of thyroid and evaluation of discordant cases

INTRODUCTION

The main role of fine needle aspiration cytology (FNAC) lies in differentiating between a malignant and benign thyroid nodule. It greatly influences the treatment decision. The current study was undertaken to evaluate the cytology-histopathology correlation and to analyze the cause of diagnostic errors with an eventual aim to improve diagnostic accuracy.

MATERIALS AND METHODS

This is a retrospective study comparing cytology and corresponding histopathology report in 724 thyroid cases. The statistical analysis included false positive rate, false negative rate, sensitivity, specificity, positive predictive value, negative predictive value and accuracy.

RESULTS

On cytological examination, 635/724 were reported as benign, 68 malignant and 21 suspicious. On histopathological examination, 626/635 cases were confirmed as benign but there were 9 discordant cases. Among the other cases histopathology diagnosis of malignancy matched in 66/68 and 11/21 cases. Diagnosis correlated in 703/724 cases (97%) [p<0.001]. False positive and false negative rates were 1.9% and 10.5%, respectively. The sensitivity and specificity were 89.5% and 98%, respectively. The positive predictive value was 84.6% and negative predictive value was 98.6%. Accuracy of FNA was 97%.

CONCLUSION

In spite of high accuracy of FNAC in differentiating between a benign and malignant lesion, certain pitfalls should be kept in mind. The common false negative diagnoses were follicular pattern cases which constitute a 'gray zone', cystic papillary thyroid carcinoma (PTC) and papillary microcarcinoma. The reason for false positive diagnoses was the occurrence of nuclear features characteristic of PTC in other thyroid lesions. Awareness of pathologist regarding these pitfalls can minimize false negative/positive diagnoses.

Expression Levels of miR-30a-5p in Papillary Thyroid Carcinoma: A Comparison Between Serum and Fine Needle Aspiration Biopsy Samples

BACKGROUND

Fine needle aspiration biopsy (FNAB) is a useful tool in the diagnosis of thyroid nodules. However, some limitations exist as approximately 25% of the cases cannot be distinguished with this method. Therefore, identification of novel diagnostic markers is very important in improving the papillary thyroid carcinoma (PTC) diagnosis. microRNAs (miRNAs) are small regulatory RNA molecules that have been involved in a variety of biological processes, including tumorigenesis. Moreover, determination of miRNAs with prognostic, diagnostic, and therapeutic potential is of a great interest today.

AIMS

In the present study, we evaluated the expression level of miR-30a-5p in serum and FNAB samples of PTC patients.

METHODS

A total of 60 cases were included in the study, with the patients subdivided into four groups; benign, atypical cells of undetermined significance (ACUS), malignant group, including Hurthle cell PTC (HC-PTC), and malignant without Hurthle cell PTC (non-HC-PTC). Peripheral blood and FNAB samples of the cases were collected. The serum and FNAB expression levels of miR-30a-5p among the groups were compared. The miR-30a-5p expression level was determined using real-time polymerase chain reaction (RT-PCR).

RESULTS

According to both pre- and postoperative pathological diagnosis, miR-30a-5p levels were significantly increased in both serum and FNAB samples of HC-PTC and non-HC-PTC groups compared to other groups. This increase was more evident in the non-HC-PTC group (p=0.0245 for FNAB, p=0.0166 for serum).

CONCLUSIONS

The results of this study suggest that miR-30a-5p might be a novel diagnostic marker candidate in PTC. Further studies are required to investigate this possibility.

Preoperative Evaluation of Thyroid Epithelial Lesions by DNA Ploidy and Galectin-3 Expression in FNAC

AIM: This study aimed to investigate the value of DNA ploidy and galectins-3 immunostain in the preoperative evaluation of thyroid epithelial lesions.MATERIAL AND METHODS: Sixty patients presenting with thyroid enlargement were included in this study and referred by clinicians for FNA. Routine cytological evaluation was done on PAP   stained slides according to the WHO criteria and at least three slides were prepared for routine cytological examinations. The nuclear DNA analysis was performed at the Pathology Department, National Research Center using the Leica Qwin 500 Image Analyzer (LEICA Imaging Systems Ltd, Cambridge, England). Galectin-3 expression was investigated in all tissues using streptavidin-biotin technique.RESULTS: Conventional Fine needle aspiration cytology (FNAC) of 60 cases could diagnose malignancy with a sensitivity of 60%, negative predictive value (NPV) 71.4%, and overall diagnostic accuracy of 80%. The aneuploidy was significantly associated with malignancy, with sensitivity 90.9%, specificity 83.3% and accuracy 88.3%. On using galectin-3 immunocytochemichal stain on cell blocks prepared from FNA the values were improved, sensitivity 93.3% specificity 86.7% and overall accuracy 90% and it was noticed that galectin-3 over expression was significantly associated with malignancy.CONCLUSIONS: From the results of this study we can consider that DNA ploidy and Galectin-3 could refine the FNA results and  increase its sensitivity as a screening test from sensitivity(60%) to reach sensitivity (93.3%), thus decreasing the false negative cases. From this study, it is concluded that the application of ancillary techniques as galectin-3 immunocytochemical markers may become a reliable indicator for surgical intervention, DNA ploidy measurements on the other hand may be of value in galectin-3 negative cases to determine the behavior of the lesion in such cases & refine the preoperative assessment by out ruling false negative cases.

Variants of papillary thyroid carcinoma: association with histopathological prognostic factors

Papillary carcinoma is the most common thyroid malignancy. Many variants of this tumor have been described, with different morphological and molecular characteristics. Although most cases have excellent prognosis, the relationship between tumor architecture and its biological behavior remains controversial.

Objective

To present the experience of a single center on the prevalence of thyroid papillary carcinoma variants and their relationship with other histopathological prognostic factors.

Method

Retrospective study of all the cases submitted to thyroidectomy for papillary carcinoma in the same institution over 11 years.

Results

We included 517 patients, 81.9% of them were women. The average age was 47.2 years. The variants recognized to have higher aggressiveness potential corresponded to 5.6% of the sample. We found an association of tumor subtypes with greater lesion diameter, T staging, lymphovascular and gland capsule invasion.

Conclusion

A small percentage of papillary carcinoma cases is represented by variants recognized by their greater potential for aggression. There are associations between these variants and several other histopathological factors already recognized for their prognostic value, which may, by themselves, influence the outcome of these cases.

Malignancy rate of thyroid nodules defined as follicular lesion of undetermined significance and atypia of undetermined significance in thyroid cytopathology and its relation with ultrasonographic features

Fine-needle aspiration biopsy (FNAB) has been widely accepted as the most accurate, safe, and cost-effective method for evaluation of thyroid nodules. The most challenging category in FNAB is atypia of undetermined significance (AUS) and follicular lesion of undetermined significance (FLUS). The Bethesda system (BS) recommends repeat FNAB in that category due to its low risk of malignancy. In our study, we aimed to investigate the malignancy rate of thyroid nodules of AUS and FLUS and whether there were different malignancy rates among the different patterns in this category, and to evaluate the presence of biochemical, clinical, and echographic features possibly predictive of malignancy related to AUS and FLUS. Data of 268 patients operated for AUS and FLUS cytology were screened retrospectively. Ultrasonographic features and thyroid function tests, thyroid antibodies, scintigraphy, and histopathological results were evaluated. Of the 268 patients' results, 276 nodules are evaluated. Malignancy rates were 24.3 % in the AUS group, 19.8 % in the FLUS group, and 22.8 % in both groups. In the evaluation of all nodules, the predictive features of malignancy are hypoechogenicity and peripheral vascularization of the nodule. We determined that the malignancy rates in these nodules are higher than that in the literature rate. This high ratio may be due to the fact that we studied only patients who underwent surgery. The ultrasonographic features alone may be insufficient to predict the malignancy; therefore, all the clinical and ultrasonographic features must be considered in the evaluation of the thyroid nodules. In addition, we think that the recommended management of repeat FNAB in these groups must be reconsidered with the clinical and ultrasonographic features.

Risk stratification based on thyroid cytology: can we rely on national data?

PURPOSE

Determine correlation of malignancy rates between fine needle aspiration (FNA) biopsy and surgical specimen in an urban academic environment.

METHODS

Retrospective review at an academic medical center of fine needle aspiration biopsies and surgical specimens in a head and neck otolaryngology practice between 2000 and 2012.

RESULTS

Of the 74 biopsies diagnosed as follicular lesion, 34 (45.9%) were malignant. Of the 45 biopsies diagnosed as follicular neoplasm, 22 (48.9%) were malignant. These results are significantly higher than the average risk of malignancy cited by the American Thyroid Association of 5%-10% and 20%-30% for follicular lesions and neoplasms respectively.

CONCLUSIONS

The rate of malignancy based on a FNA diagnosis of indeterminate cytology (follicular lesion or follicular neoplasm) can vary greatly among different institutions. Thyroid surgeons should be aware of their local pathology practices to better guide therapy and counsel patients.

Management of thyroid follicular proliferation: an ultrasound-based malignancy score to opt for surgical or conservative treatment

This study was conducted to evaluate whether ultrasound characteristics of thyroid nodules with a known cytologic diagnosis of "follicular pattern" (indicative of follicular hyperplasia, follicular adenoma or follicular carcinoma) can be used to define a nodule malignancy score to limit surgery to selected, higher-risk cases. In pre-operative ultrasound results of patients diagnosed with a "follicular pattern" on cytology who subsequently underwent surgery, each nodule feature was given a score from 0 (most likely benign) to 2 (most likely malignant), resulting in a total score ranging from 0 to 11. The total nodule score (total malignancy score) was then compared with the definitive histologic diagnosis. According to our results, surgery is advisable in patients with score ≥4 (79% of carcinomas), ultrasound follow-up seems to be appropriate for patients with a score of 3 (21% of carcinomas) and no action is recommended for patients with score <3 (only benign nodules).

Radiologic and clinical predictors of malignancy in the follicular lesion of undetermined significance of the thyroid

Various ultrasonographic characteristics of thyroid nodules have been associated with a higher likelihood of malignancy, and certain clinical features may also increase the likelihood of malignancy in patients. This study is designed to determine the ultrasonographic and clinical predictors of malignancy in the atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) category. A search through the cytology files at our institution was made for cases with diagnosis of AUS/FLUS. The clinical and radiologic findings were correlated with the final surgical pathology diagnosis. A total of 140 cases of AUS/FLUS with corresponding surgical intervention were identified (112 females and 28 males). There was a 79 % malignancy rate in nodules with irregular contours, compared to 51 % in nodules with regular outlines. Nodules demonstrating calcifications showed a 57 % malignancy rate, compared to 50 % in nodules without calcifications. Sixty-one percent of cases with an ultrasonographic diagnosis of indeterminate to suspicious were malignant following surgical resection. The rates of malignancy in patients with radiation exposure, symptomatic nodules, and positive family history of thyroid cancer were 22, 59, and 33 %, respectively. BRAF mutation was demonstrated in 57 % of malignant cases and in none of benign cases. No single clinical or ultrasonographic feature or combination of features is adequately sensitive or specific to identify all malignant nodules. However, a combination of solid nodules, nodules with irregular contours, symptomatic nodules, and positive BRAF mutation has high predictive value for malignancy in patients with a cytologic diagnosis of AUS/FLUS.

The bethesda system for reporting thyroid cytopathology: a five-year retrospective review of one center experience

Fine-needle aspiration (FNA) of the thyroid gland is a widely accepted and accurate method for triaging patients with thyroid nodules. Thyroid FNA suffers from a reporting confusion due to multiplicity of category terminologies. To address this, The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) was recently introduced for unifying the terminology and morphologic criteria along with the corresponding risk of malignancy.

OBJECTIVE

The aim of this study was to report the diagnostic utility of TBSRTC at our institution and report the malignancy risk for FNA of thyroid lesions among Saudi patients using this system at KAUH (King Abdulaziz University Hospital), Jeddah, Saudi Arabia.

MATERIALS AND METHODS

A retrospective study identifying 250 thyroid FNAs performed among Saudi patients between Jan 2005-Dec 2010 was undertaken. Cytology specimen data was collected through a computerized search of our cytopathology archives.

RESULTS

Among the 250 thyroid FNAs, 84 were followed by surgical resection. The overall surgical yield of malignancy was 23.8%. The malignancy rate for the 6 categories was as follows: non diagnostic: 20%, benign: 3.1%, atypia of undetermined significance: 50%, suspicious for follicular neoplasm: 20%, suspicious for malignancy: 80%, malignant: 100%.

CONCLUSION

Retrospective classification of FNAs of thyroid lesions among Saudi patients using TBSRTC at KAAUH, Jeddah, Saudi Arabia, validates the diagnostic reproducibility of this system and yields similar results for risk of malignancy as reported by others. However the associated rates found for non diagnostic (20%) raise the possibility of malignancy risk in this category and validate the past observations that sample inadequacy is a common cause of false negative thyroid FNAs.

Incidence of malignancy in thyroid nodules determined to be follicular lesions of undetermined significance on fine-needle aspiration

BACKGROUND

Fine-needle aspiration (FNA) for thyroid nodules is the most important method for determining a diagnosis. The system for reporting results is based on a cytopathologic classification that stratifies the risk of malignancy.

METHODS

We retrospectively studied 197 patients who underwent FNA for diagnostic evaluation of a thyroid nodule and had their results reported as a follicular lesion of undetermined significance (FLUS) using the Bethesda classification system. The objective of the study was to analyze the incidence and histopathologic types of malignancy in these cases.

RESULTS

The final histopathologic breakdown is as follows: 65 cases (32.9%) of follicular adenoma, 81 cases (41.1%) of microfollicular adenomatoid nodule, 19 cases (9.6%) of microfollicular adenomatoid nodule on the background of thyroiditis, 17 cases (8.6%) of follicular carcinoma, 9 cases (4.6%) of follicular variant papillary carcinoma, and 6 cases (3.1%) of classic papillary carcinoma, for a 16.2% incidence of malignancy. Beyond these diagnoses in the FNA-biopsied nodules, we observed 29 cases (14.7%) of incidental ipsilateral papillary thyroid microcarcinoma (PTM) and 13 cases (6.6%) of incidental contralateral thyroid lobe PTM.

CONCLUSIONS

This study observed a 16.2% incidence of thyroid cancer in the nodule designated FLUS compared to the 5 to 15% rate reported by the Bethesda FNA classification. The overall incidence of incidental PTM in the thyroid gland was 21.3%. These data support considering surgical intervention for at least diagnostic purposes in a patient with the FNAB diagnosis of FLUS.

The atypical thyroid fine-needle aspiration: past, present, and future

Thyroid fine-needle aspiration has developed into a key test in the evaluation of thyroid nodules. Although the interpretation of thyroid aspirates containing mild abnormalities is problematic, the introduction of the atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) category in The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) has helped to delineate such cases in a systematic and clinically meaningful manner. Herein the authors review the cytomorphologic features associated with the AUS/FLUS interpretation and summarize the results of studies conducted since the implementation of TBSRTC.