Role of Ultrasonography in the Evaluation of Thyroid Nodule with Fine Needle Aspiration Cytology ( FNAC) Correlation

Introduction: Thyroid nodules are commonly encountered pathologies worldwide. High-resolution ultrasonography is the first-line investigation for the evaluation of thyroid nodules as it is a cheap, quick, non-invasive, easily accessible modality without radiation hazards. Our major concern is to select suspicious thyroid nodules and early detection of malignancy. Fine needle aspiration cytology (FNAC) when correlated with ultrasonographic imaging features helps inaccurate assessment of categorizing thyroid nodules. USG guided FNAC is a widely practiced procedure because it is a less time-consuming simple procedure and helps to locate suspicious sites more precisely to get a higher yield. Methods: Total 70 patients with thyroid nodules detected by ultrasonography dated from October 2020 till September 2021 were enrolled in the study. The enrolled patients had FNAC in the same settings. The ultrasonographic characteristics of thyroid nodules were assessed and correlated with cytology reports. Results: Amongst 70 patients, 84.3% were female and 15.7% were male with a male:female ratio of 1:1.8. The mean age was 48.6 ± 13.2 years. Out of 70 patients, 49 patients had benign nodules while 21 patients had malignant nodules. Nodules that have characteristics like ill-defined border, hypoechoic echotexture, having predominantly solid components, microcalcification, increased central vascularity, and absence of halo are good indicators of malignancy. The sensitivity, specificity, positive, negative predictive value, and accuracy of ultrasonography were 72%, 91.8%,78.9%, 88.2%, and 85.7 % respectively. Conclusion: Ultrasonography is the most accurate, sensitive, and specific modality in categorizing thyroid nodules. A significant correlation of p< 0.05 was observed between ultrasonography with FNAC resulting in good accuracy. There is less chance of missing malignancy which helps to reduce unnecessary surgeries and promotes surgical intervention.


INTRODUCTION
Thyroid nodules are a common condition and are found in 3%-8% of the general population. About 10-41% of clinically unapparent thyroid nodules can be diagnosed by the help of ultrasound. Females are more commonly affected by thyroid nodules. 1 Malignant thyroid nodules account for 10% of nodules while 90% of them are benign. In the case of a solitary thyroid nodule, malignancy incidence ranges between 10% and 30%. 2 Early and accurate diagnosis of a malignant thyroid nodule is a challenging role because malignant nodules have a good prognosis after excision. Ultrasonography (USG) and fine-needle aspiration cytology (FNAC) is the most useful diagnostic modalities for assessing thyroid nodules. USG has many advantages as it is noninvasive, lacks radiation, cheap, easily accessible modality, and helps classify, categorizing the nodules due to its superior resolution. Further, it also detects clinically inapparent nodules and can guide FNAC of thyroid nodules. 3 It can detect suspicious thyroid nodules that may require subsequent thorough examination and adequate treatment on time. 4,5 FNAC on other hand is simple, the most accurate screening method of assessment and diagnosis of the thyroid nodules. The surgical yield of carcinoma has been roughly doubled. The number of thyroidectomies has been reduced by 50% with a reduction of overall medical cost by 25% Overall management and treatment modality of a thyroid nodule is directly influenced by cytological examination. 4,5

METHODS
A prospective study of 70 patients was conducted from October 2020 till September 2021 in the Department of Radiology of Hospital. Detailed patient information and proper clinical history were documented. Grayscale, power, and color Doppler ultrasound imaging were performed in Aplio 400 and Xario prime ultrasound Toshiba machine using 7 MHZ high-frequency transducers.
Thyroid nodules were assessed according to margin, echogenicity, calcification, internal vascularity, internal contents, circumferential halo, and associated lymphadenopathy. The margin was divided into a well-defined and ill-defined border. The echogenicity of the lesion as compared to the thyroid gland is termed hypoechoic(lower echogenicity to that of the thyroid gland), hyperechoic (more echogenic to that of the thyroid), and isoechoic (same echogenicity as that of the thyroid gland). Calcification was termed microcalcification( measuring about 10 mm) and macrocalcification( measuring more than 10 mm). The presence of central and peripheral vascularity was noted. Internal contents were recorded as solid or cystic areas within thyroid nodules. The absence or presence of circumferential halo was also documented. FNAC of clinically apparent thyroid nodule was performed by a pathologist and under ultrasound guidance in cases of clinically inapparent nodules. It was performed by a 10 cc syringe and air-dried smears along with ether fixed wet smear were prepared. Sensitivity, specificity, positive, negative predictive values of ultrasonographic characteristics on benignity and malignancy were calculated with help of cytological examination.

RESULTS
In a prospective study of a total of 70 patients, 59 (84.3%) were female and 11 were male (15.7%) with a male: female ratio of 1:1.8. Age was ranging from 20 to 76 years with a mean age of 48.6 ± 13.2 years. Among total patients, 49 patients had benign nodules and 21 had malignant nodules. Malignancy was detected in 18 female patients and three males patients. While eight male patients and 41 female patients had benign nodules. There was a significant correlation between ultrasonographic features with FNAC reports as evidenced by a p-value of < 0.05. In our study, there was a significant correlation between ultrasonographic and FNAC findings in the differentiation of NJMS VOL 6 No. 2 ISSUE 12 July-December; 2021

CONCLUSION
Ultrasonography is the most accurate and specific modality in differentiating benign from malignant nodules and is the best imaging modality after clinical examination due to the superficial location of the thyroid gland. The combination of ultrasonography with FNAC, rather than a single modality, helps detect malignant nodules and timely surgical intervention. In addition, ultrasound also allows visualization of whole thyroid glandular parenchyma and local invasion to adjacent neighboring structures along with cervical lymphadenopathy in suspicious cases.