Thyroid disorders rank among the most prevalent endocrine diseases in India, affecting an estimated 42 million individuals, accounting for approximately 8.5% of the population [1-3]. Thyroid swellings are a frequent clinical finding in ENT and surgical outpatient departments (OPDs). The spectrum of thyroid pathology ranges from benign physiological enlargement and solitary nodules to life-threatening conditions such as thyrotoxic crises. A thyroid nodule is defined as a discrete lesion within the thyroid gland that is distinct from the surrounding parenchyma, either on palpation or radiological examination [4]. The reported prevalence of nodular thyroid disease varies significantly depending on the detection method—ranging from 2-6% by palpation, 19-35% by ultrasound, and 8-65% in autopsy studies [5].

Thyroid neoplasms represent one of the most common endocrine malignancies globally, constituting nearly 1% of all human neoplasms [6]. Thyroid carcinoma accounts for 1-5% of malignancies in women and less than 2% in men, with papillary carcinoma being the predominant histological subtype [7]. Given the potential for malignancy, accurate and early diagnosis of thyroid nodules is crucial for optimal management. Martin and Ellis first time reported the usefulness of thyroid FNAC in 1930 in New York [8]. Fine-needle aspiration cytology (FNAC) is a minimally invasive, cost-effective, and widely used diagnostic tool for evaluating palpable thyroid lesions [9]. However, conventional FNAC has notable limitations, particularly in non-palpable nodules, multifocal lesions, or predominantly cystic nodules, where the blind technique increases the risk of sampling errors and inadequate smears. Common drawbacks include excessive blood contamination, insufficient cellular yield, and nondiagnostic specimens, which may lead to repeat procedures or unnecessary surgical interventions.

Ultrasound guided FNAC (USG-FNAC) was first introduced by Rizatto et al. in 1973. Since then, several studies have reported that USG-FNAC reduces the inadequacy rate of conventional FNAC. [10] [11]. Previous studies [11-13] have demonstrated that US-FNAC offers superior visualization, enabling precise targeting of smaller nodules and solid components within cystic lesions in a single attempt. This reduces the need for repeated procedures and improves diagnostic accuracy. Additionally, US-FNAC provides rapid and definitive results, enhancing clinical decision-making.

Given these advantages, this study aims to compare the smear quality and diagnostic efficacy of US-FNAC with conventional FNAC in the evaluation of thyroid nodules.

Study Design and Setting

This was a descriptive cross-sectional retrospective study conducted over a two-year period (January 2023 – December 2024) in the Department of ENT, Pathology and Internal Medicine at PDU Medical College and Associated Group of Hospitals, Churu.

Study Population and Inclusion and Exclusion Criteria

All the patients of thyroid nodules who attended departemt of ENT and Internal Medicine and for whom, fine-needle aspiration cytology (FNAC) samples of thyroid nodules—both percutaneous unguided (conventional FNAC) and ultrasound-guided (US-FNAC)—received in the department of pathology during the study period were included. Patients without complete clinical records were excluded from the study.

Data Collection

• Clinical history (including patient demographics, nodule characteristics, and prior investigations) was retrieved from medical records.
• Radiological findings (where available) were reviewed for nodule size, location, and sonographic features.

FNAC Procedure and Sample Processing

• Conventional FNAC: Performed on palpable nodules without imaging guidance.
• US-FNAC: Conducted under real-time ultrasound guidance for non-palpable, complex, or small nodules to ensure precise sampling.
• Smear Preparation:
  • Aspirated material was immediately spread onto glass slides.
  • Slides were fixed in methanol and stained with hematoxylin and eosin (H&E).
• Microscopic Evaluation:
  • All smears were examined under a light microscope by experienced pathologists.
  • Smears were assessed for cellularity, blood contamination, and diagnostic adequacy based on Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) criteria.

Statistical Analysis

• Diagnostic yield, smear adequacy, and sample quality were compared between conventional FNAC and US-FNAC.
• Statistical tests (Chi-square/Fisher’s exact test) were applied where appropriate, with a p-value <0.05 considered significant.

In the present study, a total of 92 fine-needle aspiration cytology (FNAC) procedures of the thyroid gland were analyzed. Of these, 53 were performed using the conventional method (C-FNAC), and 39 were done under ultrasound guidance (US-FNAC). Of the 92 patients, 60 were female (65.22%) and 32 were male (34.78%). Among those who underwent C-FNAC, 36 (67.92%) were female and 17 (32.08%) were male. In the US-FNAC group, 24 (61.54%) were female and 15 (38.46%) were male. The gender distribution was comparable between both groups. The age of patients ranged from 12 years to 74 years with the median age of 39 years. Out of the total of 92 patients who underwent FNAC, 44 patients had cytohistological correlation. Of the 44 patients who had cyto-histological correlation, 25 underwent C-FNAC and 19 patients underwent US-FNAC.

Table 1: Gender wise distribution of cases in both groups.

The adequacy of the smears was significantly better in the US-FNAC group. Of the 53 C-FNAC smears, 44 (83.1%) were adequate and 9 (16.98%) were inadequate. In contrast, 38 (97.44%) of the 39 US-FNAC smears were adequate, and only 1 (2.56%) was inadequate. This difference was statistically significant, with a p-value of 0.02. The absolute difference in adequacy was 20.61% (95% CI: 4.292% to 34.803%). Smear quality was assessed based on the presence of blood in the background, adequacy of cellularity, and presence of only serous fluid. These results demonstrate a superior smear quality in the US-FNAC group, particularly with significantly fewer bloody and hypocellular smears. [Table no. 2]

Table 2: Comparison of quality of smear indicators in both groups.

Benign lesions were predominant, with colloid and nodular goitres accounting for 66.3% of cases. Malignancies (follicular neoplasms, papillary and anaplastic carcinoma) were diagnosed in 8 cases (8.6%). [Table no. 3]

Table 3: The distribution of cytological diagnoses among all 92 cases was as follows:

On histological examination in the cases where histopathology was sent and reports were available, 4 cases out of 53 of conventional FNAC were discordant on histopathological examination. Three cases of lymphocytic thyroiditis on cytology were reported as papillary carcinoma of thyroid showing false negative results on FNAC. One case reported as Papillary thyroid carcinoma on FNAC was reported to be nodular goitre on histopathological examination (false positive). However, all the cases of US guided FNAC were confirmed on histopathological examination. It was seen that both US-FNAC, C-FNAC, and overall, the specificity and negative predictive value is high. Three cases of papillary carcinoma were missed among the group who underwent conventional FNAC, and we observed sensitivity – 82.9%, specificity - 100%, accuracy - 96%, positive predictive value - 100%, negative predictive value - 95% in diagnosing malignancies by conventional cytology.

Fine-needle aspiration cytology (FNAC) is well established as a simple, cost-effective, and minimally invasive diagnostic procedure for evaluating thyroid lesions. It offers high sensitivity and specificity, making it a valuable first-line investigation for both palpable and non-palpable thyroid nodules. [12–15] Conventional FNAC (C-FNAC), however, is a blind technique, and its diagnostic accuracy depends largely on the expertise of the operator. Ultrasound-guided FNAC (US-FNAC) overcomes these limitations by enabling real-time visualization of the lesion, thereby improving sample localization, especially in small, deep-seated, or partially cystic nodules. This increased precision minimizes the need for repeat aspirations, reduces non-diagnostic samples, and ultimately improves diagnostic accuracy [11,12].

In our study of 92 thyroid FNAC cases, 53 were performed using the conventional approach and 39 under ultrasound guidance. The patient population showed a clear female predominance (65.22%), which is consistent with the known higher incidence of thyroid disorders in females and supported by earlier findings from Sajikumar NR et al. [16] and B.R. Ashwini et al. [12]

Cytological evaluation revealed that benign lesions were most common, comprising 88.04% of cases, with colloid goitre and nodular goitre being the predominant diagnoses. Malignant lesions were detected in five cases (5.43%)—including papillary and anaplastic carcinoma—all of which were identified using US-FNAC. This distribution reflects trends reported in previous studies, including those by Likhar et al. [17] and Dr. Poorva Kalsariya [18], where benign thyroid conditions were more prevalent than neoplastic or malignant lesions.

 Smear quality analysis further reinforced the benefits of US-FNAC. Bloody backgrounds were observed in 28.3% of C-FNAC smears versus only 10.26% in US-FNAC (p = 0.035), while inadequately cellular smears were noted in 16.98% of C-FNAC cases compared to just 2.56% in US-FNAC (p = 0.02). Although the presence of only serous fluid was more frequent in C-FNAC (5.66%) than in US-FNAC (2.56%), this difference did not reach statistical significance. Danese et. al. [19] in their study reported 8.7% inadequate smears in C-FNAC whereas 3.5% inadequate in US guided FNAC. Manoj Sharma et al [20] also reported overall higher (15.19%) inadequate report with conventional FNAC as compared to sono guided FNAC (0.58%) and the difference was statistically significant. Both the studies are in concordance with the present study.

FNAC is a valuable tool for the screening and early diagnosis of thyroid pathology, offering minimal discomfort and low risk to the patient. Our study demonstrates that the quality of smears is significantly improved with ultrasound-guided FNAC compared to the conventional blind technique.

Thyroid lesions are relatively common, and their cytological diagnostic criteria are well established. Ultrasound-guided FNAC offers a distinct advantage by enabling more precise localization of lesions, thereby enhancing diagnostic accuracy. In our study, USG-guided FNAC provided superior tissue yield and higher-quality smears compared to the conventional approach, leading to improved sensitivity and overall diagnostic reliability.

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