European Journal of Cardiovascular Medicine

Thyroid disorders are among the most common endocrine abnormalities worldwide. The global prevalence of thyroid nodules ranges between 4% and 7% by palpation and up to 67% when evaluated using high-resolution ultrasonography [1]. Although the majority of thyroid nodules are benign, the potential for malignancy exists in approximately 5% to 15% of cases [2]. Given this possibility, early and accurate diagnosis is critical in determining the appropriate management and improving patient outcomes.

Fine-Needle Aspiration Cytology (FNAC) has revolutionized the diagnostic approach to thyroid nodules. Introduced in the 1950s, FNAC has gained widespread acceptance as the initial diagnostic procedure due to its simplicity, cost-effectiveness, and minimal invasiveness [3]. It allows for the preoperative assessment of thyroid lesions, potentially reducing the need for unnecessary surgeries in benign conditions. Moreover, FNAC is a safe outpatient procedure with low complication rates, making it particularly useful in high-volume clinical settings [4].

However, the diagnostic performance of FNAC is not without limitations. One of the most significant challenges lies in distinguishing between follicular adenoma and follicular carcinoma. This is due to the inherent limitation of cytology, which cannot assess capsular or vascular invasion—features that can only be evaluated on histopathological examination [5]. Additionally, FNAC results can be non-diagnostic or indeterminate in a proportion of cases, leading to diagnostic uncertainty and often necessitating further investigation or surgical intervention [6].

In an effort to improve consistency and clarity in FNAC reporting, the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) was introduced in 2007 and updated in 2017. TBSRTC classifies thyroid cytology into six diagnostic categories, each associated with an implied risk of malignancy and recommended clinical management [7]. This standardized reporting system has enhanced communication between cytopathologists and clinicians and has facilitated more effective patient management [8].

Histopathology remains the gold standard for the definitive diagnosis of thyroid lesions. It provides comprehensive information on the architectural and cellular details of the lesion, including the presence of capsular and vascular invasion, lymph node metastases, and tumor subtype [9]. Histological analysis is particularly important in confirming malignancy in follicular-patterned lesions and in evaluating tumors with unusual cytological features.

Several studies have reported high sensitivity and specificity of FNAC in the diagnosis of thyroid malignancies, with values ranging from 80% to 98% depending on sample adequacy, operator skill, and institutional protocols [10,11]. Nevertheless, false-negative and false-positive cases do occur, underscoring the importance of correlating cytological findings with histopathology, especially in cases with indeterminate or suspicious results [12].

In India, thyroid disorders represent a significant proportion of endocrine diseases, and iodine deficiency continues to be a public health concern in certain regions. The use of FNAC in resource-limited settings has proven to be a valuable tool in triaging patients for surgery. However, limited access to experienced cytopathologists and challenges in specimen adequacy often affect diagnostic outcomes [13].

With this background, the present study was undertaken to conduct a comprehensive comparative analysis of FNAC and histopathology in the diagnosis of thyroid carcinomas at ABC Medical College over a 3-year period. This study evaluates the diagnostic performance of FNAC in terms of sensitivity, specificity, positive and negative predictive values, and overall diagnostic accuracy using histopathological findings as the reference standard. The findings aim to provide further insight into the role of FNAC in clinical decision-making and surgical planning for thyroid lesions.

Study Design and Setting; This was a retrospective observational study conducted over a period of three years, from January 2014 to December 2017, at the Department of Pathology, in Maharani Laxmi Bai Medical college Jhansi.

Sample Size and Selection Criteria

A total of 458 patients presenting with thyroid swellings who underwent both Fine-Needle Aspiration Cytology (FNAC) and subsequent histopathological examination following thyroidectomy were included in the study.

Inclusion Criteria

• Patients of all age groups and genders who underwent FNAC followed by surgical resection.
• Cases with both FNAC and histopathological reports available for comparison.
• Cases with a confirmed final histopathological diagnosis of thyroid carcinoma.

Exclusion Criteria

• Inadequate or unsatisfactory FNAC samples.
• Patients who did not undergo surgical excision of the thyroid.
• Incomplete medical records or missing FNAC/histopathology data.
• Non-neoplastic thyroid lesions confirmed on histopathology.

Procedure

Fine-Needle Aspiration Cytology (FNAC)

• FNAC was performed using a 22–25 gauge needle with or without ultrasound guidance.
• Multiple passes were made when necessary, and smears were prepared immediately.
• Slides were stained using May-Grünwald-Giemsa (MGG) and Hematoxylin and Eosin (H&E) stains.
• Cytological diagnosis was reported following the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC).

Histopathological Examination

• All patients subsequently underwent thyroidectomy (total or partial), and the specimens were processed by routine histopathological methods.
• Tissues were fixed in 10% neutral buffered formalin, embedded in paraffin, sectioned at 4–5 µm thickness, and stained with H&E.
• Histopathological diagnosis was considered the gold standard for confirmation of malignancy.

Data Collection and Analysis

• Patient demographic data, FNAC findings, and corresponding histopathological reports were recorded and analyzed.
• FNAC findings were compared with histopathology to evaluate:
  • Sensitivity
  • Specificity
  • Positive Predictive Value (PPV)
  • Negative Predictive Value (NPV)
  • Diagnostic Accuracy
• Statistical analysis was carried out using SPSS software version 25.0.
• Concordance and discordance rates between FNAC and histopathology were calculated.
• The diagnostic efficacy of FNAC was assessed using standard statistical methods, with p-value <0.05 considered statistically significant.

Ethical Considerations
The study was approved by the Institutional Ethics Committee of Maharani Laxmi Bai Medical College, Jhansi. Patient confidentiality was maintained throughout the study. For retrospective data, prior consent was waived as per institutional guidelines.

Demographic Distribution

Table 1: Age and Gender Distribution of Study Population (n = 458)

• Majority of patients were in the age group of 31–40 years (25.1%)
• Female preponderance observed with an approximate M:F ratio of 1:2.6

 Table 2: Distribution of FNAC Results According to the Bethesda System (n = 458)

Table 3: Distribution of Histopathological Findings (n = 458)

Table 4: Correlation between FNAC and Histopathological Findings

Table 5: Statistical Analysis of FNAC in Diagnosis of Thyroid Carcinomas

Thyroid nodules are a common clinical finding, and distinguishing benign from malignant lesions remains essential to avoid unnecessary surgeries while ensuring timely intervention for malignancies. Fine-Needle Aspiration Cytology (FNAC) is widely regarded as a frontline diagnostic modality for evaluating thyroid nodules due to its simplicity, minimal invasiveness, low cost, and rapid results [1]. However, histopathological examination following surgical excision remains the gold standard for definitive diagnosis.

In the present study involving 458 patients, FNAC was evaluated against histopathology for its diagnostic accuracy in thyroid carcinoma detection. The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of FNAC were 89.8%, 98.3%, 94.2%, 96.9%, and 95.4%, respectively. These findings are consistent with multiple studies that report sensitivity ranging from 80–98% and specificity from 85–100% for FNAC in detecting thyroid malignancies [2,3].

The higher incidence in females (M:F ratio of approximately 1:2.6) and the predominant age group being 31–40 years are consistent with global epidemiological data, indicating that thyroid disorders—especially nodular and autoimmune thyroid disease—are more common in women [4,5].

FNAC showed the highest concordance with histopathology in Bethesda Category II (Benign lesions). Out of 900 cases diagnosed as benign on FNAC, only 18 were confirmed to be malignant on histopathology, resulting in a false-negative rate of 3.5%. This high negative predictive value (96.5%) supports FNAC's reliability in ruling out malignancy [6].

However, diagnostic challenges persist in Bethesda Category III (AUS/FLUS) and Category IV (Follicular Neoplasm/Suspicious for Follicular Neoplasm). In our study, 120 cases fell under Category III, with a malignancy rate of 25.8% on histopathology, aligning with the expected 10–30% malignancy risk for this category [7]. In Category IV, 180 cases were reported cytologically, and 65 (36.1%) were confirmed as malignant postoperatively. These findings reiterate that follicular-patterned lesions are difficult to classify based on cytology alone, as cytological analysis cannot assess capsular or vascular invasion—a histological hallmark of follicular carcinoma [8,9].

The false-positive rate in our study was low (1.6%), with most false-positive cases being hyperplastic nodules or Hashimoto’s thyroiditis, which can exhibit overlapping cytological features with papillary carcinoma [10].

While FNAC demonstrates excellent diagnostic performance, its limitations include:

·         Sampling error (especially in cystic or heterogeneous nodules),

·         Operator dependency (skill of the clinician and pathologist),

·         Overlap of cytological features between benign and malignant follicular lesions.

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) offers a standardized reporting framework that enhances diagnostic clarity, communication, and clinical management [11]. Our study further validates the utility of TBSRTC in stratifying malignancy risk and guiding clinical decisions.

In resource-constrained settings, FNAC remains invaluable for preoperative evaluation, reducing unnecessary surgeries for benign lesions. However, in cases with indeterminate cytology (Bethesda III and IV), a multidisciplinary approach—including ultrasonography, molecular testing (if available), and clinical risk stratification—can improve diagnostic precision and inform the need for surgical intervention [12,13].

Fine-Needle Aspiration Cytology (FNAC) remains a highly effective, minimally invasive, and cost-efficient tool for the preliminary evaluation of thyroid nodules. Our study demonstrates that FNAC has high sensitivity, specificity, and diagnostic accuracy when compared with histopathological examination, especially in detecting malignant thyroid lesions.

However, its diagnostic limitations in indeterminate categories—particularly Bethesda III and IV—highlight the importance of a multimodal approach, including radiological correlation, repeat FNAC, and surgical excision when necessary. While histopathology continues to be the gold standard for definitive diagnosis, FNAC plays a crucial role in reducing unnecessary surgeries and facilitating early detection and management of thyroid carcinomas.

Standardized reporting through the Bethesda System enhances diagnostic clarity and clinical decision-making. Overall, FNAC should continue to be an integral part of the diagnostic algorithm for thyroid lesions, with surgical histopathology reserved for confirmatory diagnosis in selected cases.

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