|Year : 2013 | Volume
| Issue : 2 | Page : 68-71
Diagnostic accuracy of fine needle aspiration cytology in thyroid lesions: A hospital-based study
Komal Singh Likhar, Rakesh A Hazari, Santosh G Gupta, Umashankar Shukla
Department of Pathology, Peoples College of Medical Sciences, Bhopal, Madhya Pradesh, India
|Date of Web Publication||16-Apr-2013|
Komal Singh Likhar
HIG-12 B, Peoples Medical College Campus, Bhanpur, Bhopal, Madhya Pradesh- 462 037
Source of Support: None, Conflict of Interest: None
Background: Fine needle aspiration cytology (FNAC) is the commonly used test for diagnosis of thyroid nodules. FNAC is a cost-effective procedure that provides specific diagnosis rapidly with minimal complications. Based on the cytology findings, patients can be subjected to surgery only in cases of malignancy, thereby decreasing the rate of surgery and its consequent complications. The purpose of our study was to find the diagnostic accuracy of FNAC in thyroid lesions and to compare it with histopathology. Materials and Methods: A retrospective hospital-based study was conducted at Department of Pathology in a tertiary care institute and associated hospital of Bhopal. Data were collected from the records of FNAC and histopathology of thyroid lesions, done in last 4 years duration. Analysis was done by entering data in SPSS software, and Chi-square test was applied to find statistical significance. Results: FNAC was done on 234 patients in 4 years duration. The most common thyroid lesions were benign [221 (94.4%)], followed by malignant only [6 (2.6%)], indeterminate [3 (1.3%)], and inadequate [4 (1.7%)]. Out of 221 (94.4%) benign thyroid lesions, 33% were simple colloid goiter, 27.6% goiter with cystic changes, 16.28% nodular colloid goiter, 10.41% lymphocytic thyroiditis, 4.53% thyroglossal cyst, 4.07% colloid goiter with hemorrhage, 0.9% were follicular adenoma, and others formed 3.17%. Out of six (2.6%) malignant thyroid lesions, three were papillary carcinoma and the other three were follicular neoplasm. Conclusions: The cytological criterion for the diagnosis of thyroid lesions as benign and malignant by FNAC is a highly reliable method for the diagnosis. FNAC showed sensitivity, specificity, and diagnostic accuracy of 100% in the diagnosis of malignant lesions like papillary carcinoma as well as thyroglossal cyst and abscess.
Keywords: Diagnostic accuracy, fine needle aspiration cytology, thyroid lesions
|How to cite this article:|
Likhar KS, Hazari RA, Gupta SG, Shukla U. Diagnostic accuracy of fine needle aspiration cytology in thyroid lesions: A hospital-based study. Thyroid Res Pract 2013;10:68-71
|How to cite this URL:|
Likhar KS, Hazari RA, Gupta SG, Shukla U. Diagnostic accuracy of fine needle aspiration cytology in thyroid lesions: A hospital-based study. Thyroid Res Pract [serial online] 2013 [cited 2020 Aug 12];10:68-71. Available from: http://www.thetrp.net/text.asp?2013/10/2/68/110588
| Introduction|| |
Fine needle aspiration cytology (FNAC), being reliable, minimally invasive, cost effective, and having high sensitivity and specificity, has been applied routinely as a useful and indispensable method to diagnose thyroid lesions. FNAC has allowed a dramatic decrease in unnecessary surgeries with thyroid nodular disease, enhancing the percentage of malignant operated nodules over 50%. 
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. As FNAC distinguishes between benign and malignant lesions quite effectively, it is the preoperative screening method of choice worldwide. Its use in recent years has resulted in a significant decrease in the number of surgeries being performed, while increasing the yield of malignant lesions of patients who have undergone surgery. 
FNAC of thyroid is firmly established as a first line diagnostic test for evaluation of goiter and the single most effective test for pre-operative diagnosis of a solitary thyroid nodule.  It is used as a routine first-line diagnostic method to assess thyroid diseases. As it is a simple technique which can be carried out in the out-patient department, it can be readily repeated if necessary and has good patient compliance. FNAC is therefore used as the key investigation in combination with radiological investigations in many recognized centers to assess discrete thyroid swellings to diagnose or exclude a malignancy. FNAC has also reduced the need of isotope scans and the necessity for surgery. Thyroid nodules that are considered for FNAC include firm, palpable, solitary nodules, nodules associated with suspicious clinical or ultrasonographic features, dominant nodules in a multinodular goiter, recurrent cystic nodules, and nodules associated with palpable lymph nodes. 
Several studies based on different methodologies have reported a high degree of sensitivity, specificity, positive and negative predictive values of FNAC for thyroid.  It has a diagnostic accuracy of over 90% in terms of predictive value, sensitivity, and specificity in the diagnosis of malignancy. Accuracy of the diagnosis has been shown to increase with the experience of the pathologist. 
This study is aimed to determine the pattern of thyroid lesions and diagnostic accuracy of FNAC in the diagnosis of thyroid lesions and to compare it with histopathology.
| Materials and Methods|| |
A retrospective hospital-based study was conducted at Department of Pathology in a tertiary care institute and associated hospital of Bhopal. Data were collected from the records of FNAC of thyroid lesions done in 4 years from June 2008 to May 2012. Inclusion criteria were all patients with thyroid lesions who had undergone FNAC on out-patient and in-patient basis in the cytology section. FNAC results were then compared with the available histopathologic results to find the diagnostic accuracy of FNAC.
Fine needle aspiration (FNA) was done with a 22- or 23-gauge needle attached to a 20 cc airtight disposable syringe fitted in a syringe holding FNA Gun which provides better grip and negative pressure to aspirate adequate sample. The sample was obtained by to and fro motion. Samples were smeared onto glass slides and fixed in 95% methanol, along with one or two air-dried smears for May Grunwald Giemsa (MGG) stain. In cystic lesions, after aspiration of fluids, the lesion was again aspirated. The fluid was centrifuged and smears are made from sediment. Wet-fixed smears were stained with Hematoxylin and Eosin (H and E) and Papanicolaou stains, while air-dried smears were stained with MGG stain. The cytology results were categorized into four groups: inadequate, benign, indeterminate, and malignant. Data were entered in SPSS software and analysis was done. Chi-square test was applied to find statistical significance.
| Results|| |
The study aims to determine the cytological pattern of thyroid lesions and the diagnostic accuracy of FNAC as initial diagnostic method in the investigation of thyroid swelling. Totally 234 patients had undergone FNAC and 27 patients had undergone histopathology also of thyroid in 4 years duration from June 2008 to May 2012 on OPD basis.
The most common thyroid lesions were benign in 221 (94.4%), followed by malignant only in 6 (2.6%), indeterminate or suspicious in 3 (1.3%), and inadequate for cytological assessment in 4 (1.7%) as per [Table 1]. FNAC categories benign, malignant, indeterminate, and inadequate were found to be significantly associated with age. Benign thyroid lesions were more common in 21-30 years age group, while malignant thyroid lesions were common in 30-60 years age group.
Gender distribution of thyroid lesions showed female preponderance, with 86.3% females and 13.7% males and a male: female ratio of 1:7. There was significant association found between benign and malignant thyroid disease with gender, and was higher toward the female side.
Out of 221 (94.4%) benign thyroid lesions, 33% were simple colloid goiter, 27.6% colloid goiter with cystic changes, 16.28% nodular colloid goiter, and 10.41% were lymphocytic thyroiditis. Also, thyroglossal cyst formed 4.53%, colloid goiter with hemorrhage 4.07%, follicular adenoma 0.9%, and others formed 3.17% (which include thyroid cyst, abscess, and Hurthle cell adenoma). Out of six (2.6%) malignant thyroid lesions, three were papillary carcinoma and the other three were follicular neoplasm.
Out of total 234 thyroid FNAC, histological correlation was done in 27 cases only. Histology confirmed 26 benign lesions of FNAC into simple colloid goiter 5 (18.52%), nodular colloid goiter 13 (48.15%), colloid goiter with cystic changes 6 (22.22%) and rest lymphocytic thyroiditis, thyroglossal cyst & others comprise 1 (3.70%) each as per [Table 2]. Out of 6 malignant lesions histology was done in 1 case only, which confirmed the diagnosis by FNAC. Histological correlation was possible in only one malignant lesion because all cases diagnosed as malignant by FNAC were referred to the cancer hospital.
When FNAC and histopathology results were compared, FNAC showed sensitivity, specificity, and diagnostic accuracy of 100% in the diagnosis of malignant lesions like papillary carcinoma as well as thyroglossal cyst and abscess.
Sensitivity, specificity, and diagnostic accuracy of FNAC were 50%, 94.74%, and 81.48%, respectively, in the diagnosis of simple colloid goiter, and 100%, 70%, and 77.78%, respectively, in the diagnosis of nodular colloid goiter. Sensitivity, specificity, and diagnostic accuracy of FNAC were 66.67%, 100%, and 88.89%, respectively, in the diagnosis of colloid goiter with cystic change as per [Table 3].
| Discussion|| |
A study by Beneragama analyzed the FNAC reports and histopathology reports of 158 patients with thyroid diseases.  Histological and cytological analysis showed 83 (54.60%) non-neoplastic conditions and 69 (45.39%) neoplastic conditions. FNAC had an acceptable validity in the diagnosis of thyroid diseases by means of high specificity (86.74%), sensitivity (84.05%), positive predictive value (84.05%), and negative predictive value (86.74%). Colloid goiter was found to be the commonest non-neoplastic condition. Out of the neoplastic conditions, follicular neoplasms were the commonest followed by papillary carcinoma. These findings are consistent with our study as simple colloid goiter was the commonest; however, the overall percentage of benign conditions (94.45%) is much higher in our study.
Suresh Kumar at Karachi conducted a study on 89 patients with enlarged thyroid gland. Preoperative FNAC was performed by a pathologist and postoperative specimens' histopathologic diagnoses were made and correlated.  All FNAC reports were with histopathology diagnosis. Of the 89 patients, 60 were females and 29 were males. In 82 patients, FNAC showed benign lesion, of which 80 were true negative and 2 were false negative, which on histopathology were observed malignant. The remaining nine cases were diagnosed as malignant on histopathology, of which seven were true positive. No case of false positive was detected in our study. Overall sensitivity was 77%, specificity 100%, and accuracy was 97.7.
Bagga conducted a 5-year retrospective study of FNAC of thyroid lesions during January 2004 to December 2008. The FNAC findings were correlated with the histopathologic diagnoses.  Exactly 252 patients had undergone FNAC during the study, and out of that, 4 (1.6%) were inadequate for cytological assessment, 228 (90.5%) patients had benign lesions, 17 (6.7%) had lesions that were suspicious for malignancy, and 3 (1.2%) had malignant neoplasms. The correlation of the FNAC findings with the histopathologic diagnoses showed that our FNAC diagnostic accuracy rate was 96.2%, with a sensitivity of 66% and specificity of 100%. These findings are in consonance with our study findings.
Manoj Gupta conducted a prospective study on 75 patients between January 2003 and December 2005.  All patients with clinically diagnosed solitary thyroid nodule and euthyroid subjects were included and those with multinodular goiter and who were hypothyroid or hyperthyroid were excluded from the study. The sensitivity, specificity, accuracy, false-positive rate, false-negative rate, positive predictive value, and negative predictive value of FNAC for the diagnosis of neoplastic solitary thyroid nodules were 80%, 86.6%, 13.3%, 20%, 80%, and 86.6%, respectively. Commonest malignancy detected was papillary carcinoma in 12 patients. In our study, the sensitivity, specificity, and diagnostic accuracy of FNAC in the diagnosis of nodular colloid goiter were found to be 100%, 70%, and 77.78%, respectively.
Pinki Pandey conducted a retrospective study on 447 patients with thyroid swelling during a period of 7 years and found that 322 (72.03%) were benign lesions, 84 (18.79%) were indeterminate, and 21 (4.69%) were malignant lesions. A sample of 20 (4.47%) was inadequate for FNAC. Among the benign lesions, histopathology was available in 54 cases. Cyto-histo concordance was obtained in 45 cases, whereas the remaining 9 cases showed malignant histology.  In this study, FNAC achieved a sensitivity, specificity, diagnostic accuracy, positive predictive value, and negative predictive value of 57.14%, 90%, 80.28%, 70.58%, and 83.33%, respectively. These results are similar to our study where FNAC achieved a sensitivity, specificity, and diagnostic accuracy of 50%, 94.74%, and 81.48%, respectively, in the diagnosis of simple colloid goiter.
Strength and limitations of the study
This study was a 4-year review of data from a hospital. It well describes the pattern of thyroid lesions and diagnostic accuracy of FNAC as a gold standard test for the diagnosis of thyroid diseases. Limitation of this study was that histopathology data were available in very few thyroid lesions, as compared with FNAC. All malignant diagnoses on FNAC have been referred to Cancer Hospital, and hence could not be followed up further. Similar prospective multicentric studies should be carried out to know about the relative diagnostic accuracy of FNAC over USG-guided FNAC and histopathology, and also to determine the burden as well as the pattern of thyroid diseases district wise and state wise.
| Conclusion|| |
The cytological criterion for the diagnosis of thyroid lesions as benign and malignant by FNAC is the most reliable method for diagnosis. In this study, benign thyroid lesions were the commonest found in 221 (94.4%). Out of all benign lesions, simple colloid goiter (33%) was the most common. Thyroid lesions showed female preponderance, with 86.3% females and 13.7% males and a male: female ratio of 1:7. There was significant association between benign and malignant thyroid disease with gender.
The sensitivity, specificity, and diagnostic accuracy of FNAC in the diagnosis of nodular colloid goiter were 100%, 70%, and 77.78%, respectively. FNAC showed sensitivity, specificity, and diagnostic accuracy of 100% in the diagnosis of malignant lesions like papillary carcinoma as well as thyroglossal cyst and abscess. Thus, it can be said that FNAC is the first-line diagnostic procedure for all thyroid diseases; it replaces the need for histopathology in most of the lesions. However, histopathology remains the investigation of choice for confirmation of malignancy.
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[Table 1], [Table 2], [Table 3]