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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 6  |  Issue : 2  |  Page : 129-133

Comparison of fine-needle aspiration cytology and histopathological reports of thyroid nodules: An observational study


1 Department of Surgery, Maharashtra Institute of Medical Sciences and Research, Medical College, Latur, Maharashtra, India
2 Department of Physiology, Maharashtra Institute of Medical Sciences and Research, Medical College, Latur, Maharashtra, India
3 Department of Microbiology, Maharashtra Institute of Medical Sciences and Research, Medical College, Latur, Maharashtra, India

Date of Submission15-Jul-2020
Date of Decision18-Sep-2020
Date of Acceptance05-Oct-2020
Date of Web Publication21-Dec-2020

Correspondence Address:
Abhijit Satish Rayate
Department of Surgery, Maharashtra Institute of Medical Sciences and Research, Medical College, Latur - 413 512, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcrsm.jcrsm_49_20

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  Abstract 


Context: Thyroid nodule refers to a distinct lesion within the gland that is palpably or radiologically distinct from the surrounding thyroid parenchyma. The differential diagnosis of a thyroid nodule is crucial, as malignancy necessitates surgery. Fine-needle aspiration cytology (FNAC) is the recommended initial screening test for the diagnosis of thyroid nodules according to the revised Bethesda system for reporting the thyroid cytopathology system. A well-performed FNAC and reporting by expert pathologist help to avoid unnecessary surgeries in benign nodules where only conservative management or follow-up is needed.
Aims: The aim of this study is to study the correlation between FNAC reports and final histopathological reports of specimens of thyroidectomy.
Setting and Design: An observational study at a tertiary care hospital.
Subjects and Methods: This observational study included 74 patients who were euthyroid and had undergone FNAC, thyroid surgery, and histopathology in the same institution. The results of FNAC and histopathology reports were correlated and tabulated into neoplastic and nonneoplastic categories.
Statistical Analysis Used: Descriptive analysis was carried out and presented as percentages.
Results: A total of 59 nonneoplastic lesions and 15 neoplastic lesions were found on FNAC. On histopathological examination, there were 60 nonneoplastic and 14 neoplastic lesions. Comparing the results in this study, FNAC showed sensitivity of 100%, specificity of 98.33%, the positive predictive value of 98.33%, and the negative predictive value of 100%. The diagnostic accuracy was 98.65%.
Conclusions: FNAC is the most useful, safe, accurate, relatively simple, inexpensive tool to diagnose thyroid pathology and to differentiate between neoplastic and nonneoplastic etiologies.

Keywords: Fine-needle aspiration cytology, histology, neoplastic, nonneoplastic, thyroid nodule


How to cite this article:
Warad BS, Rayate AS, Musamji MA, Barhate NR, Gavkare AM, Nagoba BS. Comparison of fine-needle aspiration cytology and histopathological reports of thyroid nodules: An observational study. J Curr Res Sci Med 2020;6:129-33

How to cite this URL:
Warad BS, Rayate AS, Musamji MA, Barhate NR, Gavkare AM, Nagoba BS. Comparison of fine-needle aspiration cytology and histopathological reports of thyroid nodules: An observational study. J Curr Res Sci Med [serial online] 2020 [cited 2021 Jan 16];6:129-33. Available from: https://www.jcrsmed.org/text.asp?2020/6/2/129/304206




  Introduction Top


The term “thyroid nodule” refers to a distinct lesion within the thyroid gland that is palpably or radiologically distinct from the surrounding thyroid parenchyma. Thyroid nodules are common, seen in about 8.5% of the population.[1] They are common among women. In India, the prevalence of a palpable thyroid nodule in the community is about 12.2% according to recent studies.[2] Mostly an incidental finding, the thyroid nodule is usually asymptomatic. The patients seek medical advice due to cosmetic deformity or present with compressive symptoms or change of voice. The incidence of thyroid nodules has been on the rise in recent decades, mainly due to the widespread use of neck imaging.

The age-long controversy in the management of thyroid swelling has been centering around the satisfactory treatment on one side and some degree of morbidity associated with extensive surgery even in expert hands on the other. The strategy of management is formed after a detailed history taking, a thorough clinical examination, biochemical assessment, ultrasonography, and fine-needle aspiration cytology (FNAC). The differential diagnosis of a thyroid nodule is crucial, as malignancy necessitates surgery, while strict patient follow-up is usually necessary in benign and nonneoplastic cases.[3] Nonneoplastic disorders such as colloid goiter, cysts, developmental cysts, inflammatory lesion, dominant cyst in multinodular goiter, and benign lesion of follicular adenoma can present clinically as a solitary nodule.

FNAC is the recommended initial screening test for the diagnosis of thyroid nodules.[4] The American Thyroid Association and National Comprehensive Cancer Network state that FNAC should be used as an initial diagnostic test because of its superior diagnostic reliability and cost-effectiveness, before both thyroid scintigraphy and ultrasonography.[5],[6],[7]

FNAC is a simple, cost-effective, readily repeatable, and quick to perform procedure in the outpatient department with excellent patient compliance. Adequate representative specimen and reporting by expert pathologist make FNAC, the gold standard test to differentiate between various thyroid nodules.

FNAC is, however, not without limitations; accuracy is lower in suspicious cytology and for follicular neoplasms.[8]

Pitfalls in FNAC of the thyroid as mentioned by Shaha et al. are adequacy of specimens (quantitative and qualitative), the accuracy of specimens (nonhomogeneity of needle placement), the accuracy of cytopathological interpretations, cysts (difficulties with degenerative nodules), follicular lesions (benign vs. malignant), Hurthle cell lesions (benign vs. malignant), and lymphocytic lesions (lymphocytic thyroiditis vs. lymphoma).[9]

Despite this observation, a well-performed FNAC and reporting by expert pathologist help to avoid unnecessary surgeries in nonneoplastic and benign nodules where only conservative management or follow-up is needed.

The present study was conducted to study the correlation between FNAC reports and final histopathological reports of specimens of thyroidectomy.


  Subjects and Methods Top


The present study is an observational study in which only the analysis of the reports of the included patients was done. Approval from the Institutional Ethics Committee was obtained. The present study was conducted in the department of surgery at a tertiary care hospital from January 2017 to December 2019. In this study, we have included 74 patients who were euthyroid and had undergone FNAC, thyroid surgery, and histopathology in the same institution. Age-wise distribution is shown in [Table 1]. Two senior cytopathologists and other junior cytopathologists from our tertiary care center had reported all the slides of FNAC and histopathology in a well-coordinated agreement to avoid reporting bias. FNAC results were categorized according to the 2017 Bethesda System for Reporting Thyroid Cytopathology,[10] as shown in [Table 2]. For analytical purposes, we have considered all category-II lesions as nonneoplastic and categories-III, IV, V, and VI as neoplastic. [Table 3] shows the comparison between the results of FNAC and histopathology reports. We have tabulated and statistically analyzed the data using Microsoft Excel and Statistical Package for the Social Sciences (SPSS) software, version 22. (IBM Corp., Armonk, NY).{Table 1}{Table 2}{Table 3}

We have defined the statistical parameters for our study. Sensitivity was defined as the ability of FNAC to detect neoplastic nodule (true positive) in patients who really had thyroid neoplasm. Specificity was defined as the probability of being FNAC-negative (nonneoplastic lesion) when there were no neoplastic changes on histopathology. Accuracy is the proportion of the correct results (true positive and true negative) in relation to all cases studied. Positive predictive value (PPV) is the probability of having neoplastic thyroid disease following a positive FNAC finding. Negative predictive value (NPV) is the probability of not having neoplastic thyroid disease following negative FNAC findings.


  Results Top


In our study, most patients were from the age group of 40–60 years. The youngest was 18 years, whereas the eldest was 85 years old. In the present study, out of 74 patients, 64 (86.49%) were women and 10 (13.51%) were men. Apart from swelling in front of the neck, only six patients had a history of mild dull pain over the swelling without any specific pattern or other associated symptoms. Only three patients complained that there was difficulty in deglutition, but clinically, no signs of compression were noted.

We came across three incidences wherein the first attempt at FNAC was nondiagnostic (category-I). The findings of repeat-FNAC under sonographic guidance were suggestive of category-II in these cases. Then, such patients cannot be still reported as category-I since thyroid surgery should not be performed based on a category-I FNAC report.

Most patients (59) belonged to category-II (benign lesions), amounting for 79.73%. One smear yielded follicular lesion of undetermined significance (FLUS) hence labelled as category-III. Eleven patients (14.86%) were reported as category-IV (follicular neoplasm in 13.51% and Hurthle cell lesion in 1.35%). One report was suspicious of malignancy (category-V). Two reports (2.71%) showed papillary carcinoma on FNAC smears (category-VI). Thus, there were 59 (79.73%) cases reported as non-neoplastic and 15 (20.27%) cases reported neoplastic on FNAC [Table 2].

On histopathology, out of the 59 cases of nodular goiter, 25 cases showed colloid goiter, 24 cases showed cystic degeneration in goiter, and 10 cases showed multinodular goiter (MNG). One case of FLUS on FNAC was found to be papillary carcinoma on histopathology. Out of the 10 cases showing follicular neoplasm on FNAC, eight were reported as follicular adenoma on histopathology, whereas one was follicular cell carcinoma. One case of follicular neoplasm on FNAC was found to be multinodular goiter on histopathology (false positive [FP] = 1). One case of Hurthle cell lesion on FNAC turned out to be Hurthle cell adenoma on histopathology [Table 3].

One case of suspicious malignancy (papillary type) on FNAC was confirmed to be papillary carcinoma. Both reports of category-VI on FNAC were consistent with papillary carcinoma on histopathological reports.

The results of FNAC and histopathology were correlated into neoplastic and nonneoplastic categories, as shown in [Table 4]. We made the following statistical calculations:{Table 4}

  • Sensitivity= (True positive [TP]/[true positive (TP) + false negative (FN)]) × 100 = 100%
  • Specificity = (True negative [TN]/[TN + FP]) × 100 = 98.33%
  • Accuracy = (TP + TN/74) × 100 = 98.65%
  • PPV = TP/(TP + FP) 100 = 93.33%
  • NPV = TN/(TN + FN) × 100 = 100%.



  Discussion Top


Thyroid nodules are commonly seen in women in the age group of 40–60 years. A higher prevalence of thyroid nodules in this age group was reported by Nepali et al. (88%), Rathod et al. (89%), and Parikh et al. (86.7%).[11],[12],[13] Our results of prevalence of 77.04% are in agreement with these studies. Furthermore, the prevalence rate of 86.49% in females is comparable to studies conducted by Nepali et al. (92% females) and Kirdak et al. (91.66% females).[11],[14]

The Bethesda classification gives straightforward guidance regarding category-II as nonneoplastic; thus, these can be managed nonsurgically unless there are cosmetic issues or compressive complications. Regarding Bethesda category-III lesions on FNAC, the American Thyroid Association recommends that if repeat FNA cytology, molecular testing, or both, are not performed or inconclusive, either surveillance or diagnostic surgical excision may be performed for an atypia of undetermined significance or FLUS thyroid nodule, depending on clinical risk factors, sonographic pattern, and patient preference.[5]

For Category-IV, American Thyroid Association recommends that if molecular testing is either not performed or inconclusive, surgical excision may be considered for the definitive diagnosis of the nodule. For category-V, American Thyroid Association recommends that if the cytology is reported as suspicious for papillary carcinoma, surgical management should be similar to that of malignant cytology, depending on clinical risk factors, sonographic features, patient preference, and possibly results of mutational testing (if performed).[5]

Thus, considering the above issues, the patients of Bethesda Categories III, IV, and V will eventually require surgical excision where advanced molecular tests are not available or where patient himself wants surgery. Thus, we have also categorized our patients into neoplastic and nonneoplastic groups. In the present study, FNAC findings were nonneoplastic in 79.73% cases and neoplastic in 20.27% cases. Histopathology reports showed nonneoplastic etiology in 81.1% and neoplastic etiology in 18.9% cases. These findings are quite similar to most of the earlier studies which showed an almost similar pattern of nonneoplastic and neoplastic etiology.[8],[15],[16],[17],[18],[19]

The present study reported a sensitivity of 100%, a specificity of 98.33%, and PPV of 98.33%, and negative predictive value of 100%. These results are well comparable with most of the earlier studies.[8],[16],[17],[18],[19],[20]

The diagnostic accuracy of 98.65% in the present study is similar to Parikh et al. and Rout et al., who had reported diagnostic accuracy of 100% and 96.05%, respectively.[13],[15]

We have observed some limitations in our study. The study population from our center may not be representative of the general population. The study was time bound; hence, the study period was short, and sample size could not be larger. The study, being aimed at the correlation of FNAC and histopathology, we could not focus more on the characteristics of the nodule and the operative details.


  Conclusion Top


The results of the present study show that FNAC is the most useful, safe, accurate, relatively simple, inexpensive tool in diagnosing thyroid pathology. The present study justifies FNAC as the first-line diagnostic test for thyroid swelling to guide the surgeon in the management, by fairly differentiating neoplastic and nonneoplastic etiologies. FNAC should not be considered superior to histopathology in the final diagnosis of the thyroid, especially in Bethesda Categories-III and IV. High-volume studies need to be conducted for the efficacy of FNAC in Bethesda Categories-III and IV.

The expertise of a pathologist in differentiating neoplastic and nonneoplastic etiologies on FNAC is valuable to decide the need for surgical intervention. A second opinion review by another pathologist should be undertaken wherever indicated. However, with the possibilities of false-negative results, patients with benign or nonneoplastic results should be followed up and any clinical or sonological suspicion of malignancy should warrant the need for surgical intervention.

Acknowledgment

The authors express their gratitude to Dr. N.P. Jamadar (Dean) for permission and support during the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Cibas ES, Ali SZ. The 2017 Bethesda System for Reporting Thyroid Cytopathology. Thyroid 2017;27:1341-6. Available from: https://www.liebertpub.com/doi/10.1089/thy. 2017.0500. [Last accessed on 2020 Jan 05].  Back to cited text no. 10
    
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Nepali R, Banita V, Thakur G. Comparative study of FNAC and histopathology in the diagnosis of thyroid swelling. Internet J Head Neck Surg 2012;5:1-6.  Back to cited text no. 11
    
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Rout K, Ray CS, Behera SK, Biswal R. A Comparative study of FNAC and histopathology of thyroid swellings. Indian J Otolaryngol Head Neck Surg 2011;63:370-2.  Back to cited text no. 15
    
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