|Year : 2020 | Volume
| Issue : 3 | Page : 223-228
Fine-needle aspiration of thyroid and diagnostic accuracy
Preeti Singh1, Monika Rathi1, Vijay Jaiswal2, Nidhi Verma1, Priya Gupta1, Veer Karuna1, Snehlata Verma3
1 Department of Pathology, L.L.R.M. Medical College, Meerut, Uttar Pradesh, India
2 Department of Paediatrics, L.L.R.M. Medical College, Meerut, Uttar Pradesh, India
3 Department of Medicine, L.L.R.M. Medical College, Meerut, Uttar Pradesh, India
|Date of Web Publication||27-Jul-2020|
Dr. Monika Rathi
R-20, L.L.R.M. Medical College Campus, Meerut, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
BACKGROUND: Fine-needle aspiration cytology (FNAC) is widely considered as the gold standard in the assessment of thyroid lesions. The aim of this study is to determine the diagnostic accuracy of FNAC of thyroid lesions performed at our institution and correlate it with histopathological findings and also to compare our findings with that of studies from other regions of the world.
MATERIALS AND METHODS: The present study is a 1-year prospective study of FNAC of thyroid lesions performed in the pathology department of our institution during January 2014–December 2014. The FNAC findings were correlated with the histopathological diagnosis, wherever available. The records of 236 patients who had undergone FNAC during the study period were followed by histopathological evaluation wherever possible. The cytological results were classified as inadequate, benign, suspicious, and malignant. The histopathology diagnosis was classified as nonneoplastic (benign) and neoplastic (malignant).
RESULTS: The results of the FNA histological diagnosis showed that 6 (2.5%) of the patients had FNA, which were inadequate for cytological assessment, 222 (93.6%) patients had benign lesions, 4 (2.2%) had lesions that were suspicious for malignancy, and 4 (2.2%) had malignant neoplasm.
CONCLUSIONS: The correlation of FNAC findings with the histopathological diagnosis showed that our FNAC diagnostic accuracy rate was 97.55% with a sensitivity of 85.75% and specificity of 100%. The results of our study are comparable with the previous studies done and showed that FNAC is a sensitive, specific, and accurate initial diagnostic test for preoperative evaluation of patients with thyroid swelling. It is recommended as the first-line investigation.
Keywords: Fine-needle aspiration cytology, histology, thyroid
|How to cite this article:|
Singh P, Rathi M, Jaiswal V, Verma N, Gupta P, Karuna V, Verma S. Fine-needle aspiration of thyroid and diagnostic accuracy. Int J Health Allied Sci 2020;9:223-8
|How to cite this URL:|
Singh P, Rathi M, Jaiswal V, Verma N, Gupta P, Karuna V, Verma S. Fine-needle aspiration of thyroid and diagnostic accuracy. Int J Health Allied Sci [serial online] 2020 [cited 2021 Aug 5];9:223-8. Available from: https://www.ijhas.in/text.asp?2020/9/3/223/290711
| Introduction|| |
Fine-needle aspiration cytology (FNAC) is a well-established, outpatient procedure used in the primary diagnosis of thyroid swellings. Most of the thyroid swellings are benign. A combination of diagnostic tests such as ultrasound, thyroid nuclear scan, and FNAC is available for the evaluation of thyroid swellings. Practice guidelines set forth by 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  Bukhari et al. in their study of thyroid nodule suggest that FNAC should be adapted as an initial investigation of thyroid diseases. FNAC is simple, cost-effective, readily repeated, and quick to perform the procedure in the outpatient department (OPD) with excellent patient compliance. Most of the clinically diagnosed thyroid swellings are neoplastic, only 5%–30% are malignant and require surgical intervention. The main aim of FNAC is to identify swellings that require surgery and those benign swellings that can be observed clinically and decrease the overall thyroidectomy rate in patients with benign diseases. The study is aimed at determining the utility and diagnostic accuracy of FNAC of thyroid lesions performed at the present institution and to compare present experience with those of other studies.
| Materials and Methods|| |
This is a prospective study of 236 patients who present with diffuse or nodular thyroid swelling, referred to the pathology department of our institution, from January 2014 to December 2014. The ethical committee granted us the permission to perform this study. Forty of these 236 cases underwent surgery for a cytologically suspicious/malignant diagnosis, compression symptoms, or cosmetic reasons.
FNAC in all these patients was performed by experienced cytologists. The procedure was performed without local anesthesia with the help of the nonaspiration technique, using 23–25 gauze needles. The procedure was generally well tolerated with no significant complication. Both air-dried and wet-fixed smears (fixed in 95% alcohol for 30 min) were made from the aspirated material, stained with May Grunwald Giemsa and hematoxylin and eosin stains, respectively, and examined under a light microscope.
The cytology results were categorized into present groups – inadequate, benign, suspicious, and malignant. The histopathological diagnosis was classified as nonneoplastic (benign) or neoplastic (malignant).
Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FNAC, relative to the final histological diagnosis were analyzed using the following formulae:
- True positive (TP): Positive result in the FNAC for malignancy and confirmed in the histological study
- False positive (FP): Positive result in the FNAC for malignancy but not confirmed in the histological study
- True negative (TN): Negative result in the FNAC for malignancy and no carcinoma in the histological study
- False negative (FN): Negative result in the FNAC for malignancy, but with carcinoma in the histological study
- Sensitivity (S): Proportion of patients with associated carcinoma and a positive result in the FNAC for malignancy, S = TP/(TP + FN)
- Specificity (SP): Proportion of patients without associated carcinoma and with a negative result in the FNAC for malignancy SP = TN/(TN + FP)
- Positive predictive value (PPV): Proportion of patients with a positive result and a histological confirmation. PPV = TP/(TP + FP)
- Negative predictive value (NPV): Proportion of patients with negative results, without a carcinoma, is the histological study. NPV = TN/(TN + FN)
- Diagnostic accuracy (DA): Proportion of patients diagnosed correctly by the diagnostic test, DA = TP + TN/(TP + TN + FP + FN).
| Results|| |
A total of 236 patients underwent FNAC of thyroid swellings in the cytopathology section of the pathology department. Of these, 206 were female while 30 were male. Age of the patients ranged from 14 to 60 years. The FNAC cytology results were compared with the corresponding histological diagnosis. The FNAC results were interpreted as inadequate in 6, benign in 222, suspicious in 4, and malignant in 4 [Table 1].
|Table 1: Diagnoses in 236 thyroid swellings on fine-needle aspiration cytology|
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Thyroid FNAC results, grouped malignant (positive result), versus the rest of the diagnoses (negative results), were compared with the results of the final histological study of the excised specimen to calculate the values of the test [Table 2].
|Table 2: Distribution of benign (a), suspicious (b), and malignant (c) cases on cytology|
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Forty of these patients subsequently underwent thyroidectomy, and histopathological examination of the specimens was performed.
The histopathological findings of 40 cases that underwent surgery were benign in 34 and malignant in 6 [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]. No false-positive cases were identified. There was 1 false-negative case, given as nodular colloid goiter on cytology, which was diagnosed as follicular carcinoma on histopathology. The analysis of the results yielded a sensitivity of 85.7%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 97.5% [Table 3].
|Figure 1: Follicular carcinoma thyroid (fine-needle aspiration cytology MGG, ×100)|
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|Figure 5: Medullary carcinoma showing abundant amyloid (fine-needle aspiration cytology MGG, ×100)|
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|Figure 6: Medullary carcinoma (fine-needle aspiration cytology MGG, ×400)|
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|Figure 8: Hyperplastic goiter showing cytoplasmic eosinophilia and cytoplasmic clearing (H and E, ×400)|
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|Table 3: Correlation between fine-needle aspiration cytology and histopathology (n=40)|
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| Discussion|| |
In the present study, the age of patients ranged from 14 to 60 years with a mean of 38. This age range and mean incidence is slightly lower as compared with previous studies ,, we found that majority of patients were in their third decade of life. This is in accordance with the study by Dorairajan and Jayashree. The present study showed that thyroid swelling was seven times more common in females than males. Comparison of results of the present study with various previous studies is shown in [Table 4].
FNAC is widely accepted as the most accurate sensitive, specific, and cost-effective diagnostic procedure in the preoperative assessment of thyroid lesions. The accuracy of the FNAC analysis approaches 95% in the differentiation of the benign lesions from the malignant lesions of the thyroid gland. FNAC of the thyroid swellings is reported to have a sensitivity range of 65%–80% and a specificity of 72%–100% false-negative value of 1%–11% and a false-positive rate (FPR) of 1%–8%. In the present study, the analysis of data revealed sensitivity of 85.7% and specificity of 100%, which translates into a diagnostic accuracy of 97.5%. The results of the present study are comparable with other studies done previously.
In the present study, four cases were found to be malignant on the histopathological examination. All cases of papillary carcinoma diagnosed by FNAC were papillary carcinoma on histological examination also. This is in accordance with previous studies., The incidence of malignancy in this study was 17.5%, which is in accordance with the study by Dorairajan and Jayashree. The incidence of malignancy can be as high as 4.6%. The analysis of data from seven series showed a false-negative rate of 1%–11%, an FPR of 1%–8%, a sensitivity of 65%–98%, and a specificity of 72%–100%. The results are comparable with the present study. The present study and other studies suggest that FNAC is more specific than sensitive in detecting thyroid malignancy and therefore its use, as a reliable initial diagnostic test, cannot be overemphasized. It reduces the need for other time-consuming and expensive investigations. The false-negative rate (FNR) is defined as the percentage of patients with benign cytology in whom malignant lesions are later confirmed, after thyroidectomy. The false-negative FNAC results may occur because of sampling error or misinterpretation of cytology and are of great concern because they indicate the potential to miss a malignant lesion. In the present study, false-negative FNAC has occurred in 1 out of 40 (2.5%) patients with benign diagnosis. This is consistent with reports that suggest an FNR of 2%–7%.,
The FPR indicated that a patient with a malignant FNAC result was found on histological examination to have a benign lesion. FPR results were uncommon, and it was 0% in the present study, which was consistent with other reports that yielded FPR results ranging from 0% to 9%., In the present study, positive predictive value was 100%, negative predictive value was 97%, with a diagnostic accuracy of 97.5%, which was similar to other studies.,
We have categorized cytological results in inadequate, benign, suspicious, and malignant. As most of the benign conditions can be managed medically, it saves the patient of unnecessary surgeries.
FNAC has certain limitations on account of an inadequate sample and suspicious diagnosis. Intermediate FNAC results and cytodiagnostic errors occur commonly due to overlapping cytological features, especially with hyperplastic adenomatoid nodules, follicular neoplasms, and follicular variant of papillary carcinoma.
Among the suspicious group, 2 out of 4 (50%) cases were diagnosed as malignant on histopathology, in the present study. This is due to the limitation of thyroid cytology to distinguish follicular adenoma from follicular carcinoma. The diagnosis required a detailed histopathological examination for vascular and capsular invasion. As the incidence of malignancy in suspicious lesions was high, surgical excision of the nodules should be considered strongly in these cases. Mundasad et al. in their study concluded that suspicious and intermediate results should be reduced by diagnostic surgical resection.
Inadequate samples may be because of sclerotic or calcified lesions and also with cystic degeneration or necrosis. FNAC of 6 (25%) yielded inadequate samples. Other studies also yielded occurrence in 1%–5%. US-guided FNAC has reduced sampling errors. Pitfalls is FNAC of the thyroid as mentioned by Shaha  are as follows: adequacy of specimens (quantitative and qualitative), accuracy of specimens (nonhomogeneity of needle placement), accuracy of cytopathological interpretation, cysts (difficulties with degenerative nodules), follicular lesions (benign vs. malignant), Hurthle Cell lesions (benign vs. malignant), and lymphocytic lesions (lymphocytic thyroiditis vs. lymphoma).
These errors can be reduced by performing aspiration from different sites, with the use of the ultrasound-guided FNAC, and reporting by expert cytopathologists.
| Conclusions|| |
The results of the present study are comparable with the current published data and demonstrate that FNAC cytology is a sensitive, specific, and accurate initial diagnostic test for the preoperative evaluation of patients with thyroid swellings in the present setting as well. It is a minimally invasive, safe, and easily performed OPD procedure. It should be used as the initial modality in the evaluation of thyroid lesions.
We also concluded that FNAC diagnosis of malignancy is highly significant and such patients should undergo surgery. A benign diagnosis on FNAC should be followed up and in clinical suspicion of malignancy even in the presence of benign FNAC requires surgery.
Drawback of the study
Histopathology was available only in 40 out of 236 cases, which constitutes around 17% of the total.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2], [Table 3], [Table 4]