|Year : 2022 | Volume
| Issue : 1 | Page : 86-90
Cytological accuracy of nonguided fine needle aspiration from the thyroid - A two-year experience from southern India
Ranganath Ratnagiri1, Shubranshu Jena1, Monalisa Hui2, Shantveer G Uppin3, Rajashekar Shantappa1
1 Department of Surgical Oncology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India
2 Department of Cytopathology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India
3 Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India
|Date of Submission||15-Dec-2021|
|Date of Decision||22-Jan-2022|
|Date of Acceptance||24-Jan-2022|
|Date of Web Publication||23-Jun-2022|
Department of Surgical Oncology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana
Source of Support: None, Conflict of Interest: None
Introduction: 12.2% of the Indian have a palpable thyroid nodule, but only 5% of these are malignant. The rest of the patients do not need to undergo surgery, unless clinically indicated for other reasons. Fine needle aspiration cytology (FNA) from the thyroid gland is the most commonly performed screening investigation to determine whether a patient needs surgery or not. The sensitivity, specificity and accuracy of FNA should therefore, be audited in every Institute from their own data. Materials and Methods: A retrospective analysis of the case records of all patients of thyroid nodules who underwent surgery at our hospital between September 2019 and September 2021 was undertaken. Clinical, demographic details as well as correlation between the nonguided FNA report and the final histopathology was done. The sensitivity, specificity, positive and negative predictive value as well as accuracy of FNA was calculated. Results: The sensitivity of FNA for malignancy was 73.1% and the specificity was 89.3%. The positive predictive value was 85.7% and the negative predictive value was 79.2%. The accuracy of nonguided FNA was 81.8%. Conclusions: Though there were no inadequate smears, the high false negative rate and the lower accuracy point toward the need to use ultra-sonography guidance in selected cases to overcome the pitfalls of nonguided FNAs.
Keywords: Accuracy, nonguided fine needle aspiration, sensitivity, specificity, thyroid nodule
|How to cite this article:|
Ratnagiri R, Jena S, Hui M, Uppin SG, Shantappa R. Cytological accuracy of nonguided fine needle aspiration from the thyroid - A two-year experience from southern India. J Head Neck Physicians Surg 2022;10:86-90
|How to cite this URL:|
Ratnagiri R, Jena S, Hui M, Uppin SG, Shantappa R. Cytological accuracy of nonguided fine needle aspiration from the thyroid - A two-year experience from southern India. J Head Neck Physicians Surg [serial online] 2022 [cited 2022 Jun 28];10:86-90. Available from: https://www.jhnps.org/text.asp?2022/10/1/86/347995
| Introduction|| |
Thyroid nodules are found in about 8.5% of the Indian population, with a palpable nodule prevalent in 12.2% of the population. There is a significant female preponderance in the patient cohort. The incidence of malignancy in these thyroid nodules is about 8.7/100,000 population, or in other words, about 5% of all the people with thyroid nodules. Therefore, a test which can predict the nature of the nodule preoperatively is essential to decrease the number of “diagnostic” thyroid surgeries. Fine needle aspiration cytology (FNA) from the thyroid gland is proven to be the most effective investigation to prove the presence of cancer in a thyroid nodule. The National Cancer Institute adopted the Bethesda classification system in 2007, which categorises thyroid FNAs into six classes with malignancy risk and treatment recommendations for each category. Bethesda 3 and 4 (B3 and B4) are categories with undetermined significance and cause the maximum clinical dilemma to a surgeon.
The accuracy of a cytological diagnosis depends on the experience of the person doing the FNA, the technique used (guided or nonguided), preparation of the specimen for cytology and interpretation by the cytologist. These are variables which are extremely subjective, and every Institution needs to audit its data every once in a while, to ensure that standards are maintained and management streamlined.
The aim of our study was to determine the sensitivity and specificity of the nonguided FNAs being done for suspected thyroid malignancies in our Institute and to estimate the positive and negative predictive values as well as accuracy of the procedure in our patient population. Our objective was also to try and identify the reasons for false positive and false negative FNA reports and to rectify lacunae if any.
| Materials and Methods|| |
A retrospective analysis of the case records, the cytology reports and the final histopathology reports of all patients with suspected or proven thyroid cancer treated in our Institute between September 2019 and September 2021 was performed after obtaining approval from the Institute Ethics Committee. The demographic features of the patients (age, gender distribution, presenting complaints and medical co-morbidities) were abstracted from the records.
All patients who presented with a thyroid swelling (either a solitary nodule or with diffuse enlargement of the thyroid gland) underwent assessment of the thyroid function and a nonguided FNA at the first visit. The FNA was performed by two dedicated cyto-pathologists (in all patients) with a 26 G needle on a 10 ml syringe, with gentle negative pressure and ensuring that not more than three to four passes were made though the gland. The slides were immediately assessed for adequacy of the cells, and independently reported by the two cyto-pathologists. All reports were in line with the NCI-Bethesda system of reporting thyroid cyto-pathology (TBSRTC).
The final histopathology reports of all the patients who underwent surgery for the thyroid swelling were collected and correlated with the preoperative FNA report.
A true positive report was defined as an initial FNA report of Bethesda IV, V or VI with a final biopsy after surgery confirming malignancy. A true negative report was defined as an FNA report of Bethesda II or III with a final biopsy report of a benign pathology. False positives and false negatives were defined similarly. All patients with a Bethesda I report automatically underwent a repeat FNA and were re-categorised according to the second report.
The sensitivity, specificity, positive predictive value and negative predictive values and the accuracy of nonguided FNA done at our Institute were calculated and compared with figures available in literature.
| Results|| |
Our study included a total of 176 patients of thyroid nodules who underwent surgery after being evaluated for the same. The gender distribution was weighted in favour of females (75.5%), and the study population was exactly divided between those who were <45-year-old and those who were more than 45-year-old. Most of the patients presented with a swelling on the anterior aspect of the neck as the main complaint (86.9%), with only 14.9% of the cohort reporting either hypothyroid or hyperthyroid symptoms. The average nodule size was 4.5 ± 1.5 cm and there was no significant difference in the involvement of the right or left lobe. Pressure symptoms such as dysphagia and hoarseness of voice, both of which could have been due to malignant infiltration were reported by 11.3% of the population [Table 1].
64.7% of the FNA reports were Bethesda II and III and the rest Bethesda IV, V and VI [Figure 1]. The total number of cases with a malignant diagnosis on final histopathology was 82 (46.5%), and the rest were benign (n = 94; 53.4%). Papillary carcinoma was the most common among the malignancies (n = 62; 72.9%), followed by follicular carcinoma (n = 16; 18.5%) and four cases of medullary carcinoma [Figure 2].
|Figure 1: Distribution of the fine needle aspiration reports according to the bethesda system|
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The sensitivity of FNA as calculated from our data was 73.1% and the specificity was 89.3%. The positive predictive value was 85.7% and the negative predictive value was 79.2%. The accuracy of nonguided FNA performed at our Institute was 81.8%.
Analysis of the false negative FNA results revealed micro papillary carcinoma in nine patients, minimally invasive follicular carcinoma in Six patients and papillary carcinoma in 7 individuals [Table 3] and [Figure 3]. The 10 FNA reports which were false positive turned out to be adenomatous hyperplasia in four patients and thyroiditis in six patients.
|Figure 3: False negative fine needle aspirations correlated with final histopathology (n = 22)|
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| Discussion|| |
FNA is a simple, safe and cost-effective method which can be used in the initial screening and diagnosis of a thyroid nodule. The main aim of performing an FNA is to avoid unnecessary surgeries for nodules which are benign. The clinical value of FNA is derived from its ability to identify benign nodules and its low false negative rate, which enables clinicians to use it as an aid in surgical decision-making.
The false negative rate of nonguided FNA in our study was 12.5% [Table 2], which is comparable to the 7.5%–21% false negative rates quoted in various studies., False negative FNAs are caused either due to sampling errors – thyroid tissue adjacent to the cancer is sampled or due to the presence of an un-sampled micro-carcinoma in a large adenomatous goitre. The WHO defines papillary thyroid microcarcinoma as a papillary thyroid carcinoma (PTC) which is </=1 cm and is detected incidentally. Out of the 25 false negative reports in our study, nine patients had papillary microcarcinoma. Most authors report a higher false negative rate for larger nodules, ranging from 17.3% to 19% for nodules between 3 cm and 4 cm. Our patient population presented with an average nodule size of 4 cm to 6 cm, which probably led to the sampling errors and the false negative rate of 12.5%.
|Table 2: Depiction of the true and false positive and negative results of nonguided fine needle aspiration (n=176)|
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Interpretation errors leading to a false negative report were encountered in the seven cases of minimally invasive follicular carcinomas. Histopathologic features of these lesions may overlap with follicular neoplasms, lymphocytic thyroiditis and hyperplastic adenomas, and hence though FNA may not give us the exact diagnosis, it will point the clinician in the right direction.
The number of false positive cases (n = 10; 5.6%) was relatively low in our study compared to the literature. Lymphocytic thyroiditis in 6 cases and hyperplastic adenomatous nodules in 4 cases were the reasons established for the false positivity. Focal nuclear atypia including grooves, chromatin clearing and overlapping have been reported in hyperplastic nodules and have been shown by studies to be the reason for a false positive report of a malignant nodule. Previous studies have established lymphocytic thyroiditis as the leading cause of false positive reports in thyroid nodules. The 'cellular stage' of Hashimoto's thyroiditis is composed of oncocytic change, nuclear enlargement, fine chromatin texture, prominent nuclear membranes and macro nucleoli. All these changes mimic PTC and can be misdiagnosed as such on an FNA.
The sensitivity of FNA in our study was 73.1% and the specificity was 89.3%; the corresponding figures in literature are 82%–93.4% and 74.9%–96%. The lower sensitivity in our study can probably be explained by the slightly higher number of false negative reports, which increases the denominator while calculating sensitivity.
The positive predictive value of 85.7% compares well with the 84.3% to 98.6% value reported in other studies. The negative predictive value of our study is lower compared to literature, again due to the false negative reports.
The overall accuracy of nonguided FNA in our study (81.8%) lies within the 78.6% to 93.4% range quoted by various authors.,
| Conclusions|| |
FNA is an effective tool for screening thyroid nodules and as a pointer to performing appropriate surgery. A higher false negative rate in our study made us aware of the need for image guidance in some cases and for careful clinical, biochemical and radiologic correlation in all cases. Judicious use of image guided FNA, especially in heterogeneous nodules will reduce the number of 'diagnostic' thyroid surgeries.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
This material has never been published and is not currently under evaluation in any other peer reviewed publication.
The permission was taken from Institutional Ethics Committee prior to starting the project. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]