Study of diagnostic efficacy of USG versus FNAC for thyroid nodule at a tertiary care center

 

 

Abstract               Background: Thyroid nodular lesions are commonly seen in iodine-deficient areas in India1. Thyroid nodules are generally palpable swelling in the thyroid gland, majority are asymptomatic of these nodules, 5% are malignant. Recently ultrasonography has emerged as the best method to evaluate the thyroid gland and thyroid nodules. The purpose of this study was to compare diagnostic efficacy of ultrasonography and FNAC in evaluating thyroid nodules. Material and Methods: Present study was prospective, observational study conducted in patients with conclusive reports of FNAC and USG of thyroid nodule, coming to our tertiary care center. Results: In present study total 106 patients were included. The average age of patients was 36 years. Most common age group was 21-30 years (37 %), followed by age group 31-40 years (25 %). 83 % patients in our study were female. 82 % cases were benign, while only 18 % were malignant as per final cyto-pathological diagnosis. Colloid nodule (63 %) was most common benign lesion, while most common malignancy was papillary carcinoma (11%). Radiologically most common feature for internal composition was solid (44 %) and predominantly solid (44 %). Most lesions were hyperechoic (55 %), well defined margins (78 %), with peripheral halo (76 %), without calcification (73 %), without vascularity (78 %). FNAC had sensitivity (95 %), specificity (100 %), PPV (100 %), NPV (97 %), accuracy (97 %) while USG had sensitivity (92 %), specificity (93 %), PPV (78 %), NPV (96 %), accuracy (92 %). Conclusion: USG-thyroid should be considered as a first step and as an investigation of choice in evaluation of thyroid nodule.

Key Words: FNAC thyroid, Thyroid imaging, Thyroid malignancy

 

INTRODUCTION

Thyroid nodular lesions are commonly seen in iodine-deficient areas in India¹. Thyroid nodules are generally palpable swelling in the thyroid gland, majority are asymptomatic of these nodules, 5% are malignant, and the incidence as per recent evidence puts the percentage on the rise². Of all the thyroid nodules, 5 to 15% of them are cancerous³. As the majority of palpable thyroid nodules are benign in nature with relative rarity of malignancy, a reliable method for differentiating clinically significant malignant nodules from innocuous benign ones is desirable. Early diagnosis of malignant thyroid nodules is advocated, because of good post-surgical prognosis. Fine-needle aspiration cytology (FNAC) of thyroid nodules is the single most sensitive, specific, and cost-effective method of investigation, considered as the most reliable method for definitive evaluation of thyroid nodules^4,5. Thyroid cancer management guidelines also recommends conducting FNAC on any thyroid nodule, which is suspected to be malignant⁶. Recently ultrasonography has emerged as the best method to evaluate the thyroid gland and thyroid nodules. It is widely available, relatively inexpensive, non-invasive, has excellent resolution, detects non-palpable and clinically silent nodules, and guides for fine needle aspiration of suspicious nodules^7,8. The purpose of this study was to compare diagnostic efficacy of ultrasonography and FNAC in evaluating thyroid nodules.

 

MATERIAL AND METHODS

Present study was prospective, observational study conducted at XXX medical college, XXXX, India. Study was jointly conducted at department of pathology and department of radiodiagnosis. Study duration was one year between July 2018 and July 2019. Approval was taken from our institutional ethics committee. Patients underwent ultrasonographic evaluation of the thyroid gland and detected to have thyroid nodule, were subjected to further evaluation with fine needle aspiration cytology (FNAC). A written informed consent was obtained from all patients for participation in present study.

• Inclusion criteria

Patients in whom conclusive reports of FNAC and USG were present, willing to follow up and willing to participate were included in study.

 

 

 

• Exclusion criteria

Patients who were not evaluated with FNAC, or had inadequate or indeterminate FNAC reports, inconclusive USG report, not willing to follow up or not willing to participate were excluded from study.

Patients with diffusely enlarged glands with multiple nodules and no intervening normal parenchyma were classified as multinodular goitre were also excluded. A total of 106 patients were considered for the study, satisfying inclusion and exclusion criteria. All scans were performed on Ultrasound equipment using a high frequency 5–12 MHz probe. Patients who underwent surgical excision, specimen were sent for histologic evaluation. FNAC was done as an OPD procedure by pathologist. These ultrasonographic findings were tabulated and correlated with the final pathological diagnosis. The data thus obtained was entered into Microsoft Excel spreadsheet, and the sensitivity, specificity and accuracy for each of the findings were calculated.

RESULTS

In present study total 106 patients were included. The average age of patients was 36 years. Most common age group was 21-30 years (37 %), followed by age group 31-40 years (25 %). 83 % patients in our study were female.

 

TABLE 1: Distribution of subjects by age and sex

82 % cases were benign, while only 18 % were malignant as per final cyto-pathological diagnosis. Whenever histopathology report was available, that report was considered in final cyto-pathological diagnosis. Colloid nodule (63 %) was most common benign lesion, other were follicular adenoma (8%), Hashimoto’s thyroiditis (4%), subacute thyroiditis (2%), cyst (6%). Most common malignancies were papillary carcinoma (11%) followed by follicular carcinoma (4%), medullary carcinoma (2%), anaplastic carcinoma (1%).

 

Table 2: Final cyto-pathological Diagnosis

Radiologically features were compared in accordance to cyto-pathological diagnosis. Most common feature for internal composition was solid (44 %) and predominantly solid (44 %). Most lesions were hyperechoic (55 %), well defined margins (78 %), with peripheral halo (76 %), without calcification (73 %), without vascularity (78 %). Malignancy was noted when combination of factors such as solid and predominantly solid internal composition, hypoechoic, ill-defined margins, with peripheral halo, with calcification, with vascularity were present.

Table 3: radiological features

Statistically we compared diagnostic efficacy of USG and FNAC for evaluation of thyroid nodule. FNAC had sensitivity (95 %), specificity (100 %), PPV (100 %), NPV (97 %), accuracy (97 %) while USG had sensitivity (92 %), specificity (93 %), PPV (78 %), NPV (96 %), accuracy (92 %).

 

Table 4: Diagnostic Test Statistics of USG and FNAC for evaluation of thyroid nodule

 

DISCUSSION

A thyroid nodule is defined as a discrete lesion within the thyroid gland that is distinguishable from the adjacent parenchyma at USG. In our study, the youngest patient was 16 years old and the eldest patient was 73 years. The average age of patients and age distribution in our study was similar to that of the previous studies⁹. From total of 106 cases, female preponderance (female: male ratio of 4.88:1) was observed in the present study. The observations are similar to the female: male ratio, noted in other studies as 5.9:1, 5.4:1 and 3.4:1 in the studies by Sharma et al¹⁰ and Chen et al¹¹ respectively. Basic use of sonography in the thyroid nodule evaluation is to determine the location of palpable neck mass, characterize nodule as benign or malignant, know about extent of thyroid malignancy, and guide fine needle aspiration of the thyroid nodule or cervical lymph node. The categorization of thyroid nodules into benign and malignant nodules by USG is very important as it helps in the further management of the patients with nodular thyroid disease. Ultrasound has become the first‑line imaging modality for the evaluation of the thyroid gland due to excellent visualization of the thyroid parenchyma¹². It is highly sensitive in detective small nodules, calcification, septations, and cysts as well as in guiding fine needle aspiration biopsies. Thyroid nodules are very common and may be observed at USG in 50% of the adult population¹³. We noted 82 % cases as benign thyroid nodules, while 18 % were malignant. Most common benign pathology in our study was benign colloid goitre seen in 63% cases. In a study by Bumiya and Roopa¹⁴, benign pathology was observed in 90% cases, amongst which the commonest was goitre (66%) patients. A nodule with relatively decreased in echotexture compared to the adjacent strap muscles of the neck is considered hypoechoic. The previous similar studies have revealed that most malignancies demonstrate a hypoechoic nodule, yet most hypoechoic nodules are benign in view of the high prevalence of benign lesions^5,15. The peripheral halo is usually complete and thin. It is irregular, thick, and incomplete or absent in a malignant nodule and is thought to represent compressed normal tissue due to the rapid growth of the tumor¹⁶. The most of the studies have reported a low sensitivity and specificity for the presence or absence of a halo¹⁷. Previous studies noted that well-defined margins, well-defined thin peripheral halo, and wider than tall in shape and absence of calcifications or microcalcifications are the sonographic criteria for predicting benign nature of a thyroid nodule^15,17. In our study, ultrasound had sensitivity (92 %), specificity (93 %), PPV (78 %), NPV (96 %), accuracy (92 %). In a study by Popli¹⁷ et al., the sensitivity was 81.8% and specificity was 87.2%. Fine needle aspiration cytology appears to be a safe, reliable, accurate and cost-effective method which provides valuable information to assist in selection of patients with solitary thyroid nodules for surgery. FNAC also distinguishes the benign from malignant lesions quite effectively preoperatively, it has been proposed as a preoperative screening method of choice¹⁸. Although needle biopsy can be performed easily, consistently obtaining adequate tissue and processing the specimens to achieve accurate cytopathological interpretation requires expertise and experience¹⁹. FNAC specimens are classified as malignant, benign, indeterminate (suspicious for follicular or Hurthle cell neoplasm), or insufficient for diagnosis. The effectiveness of FNAB of solitary thyroid nodules may be improved with the use of ultrasound guidance rather than simple palpation²⁰. In our study, from 106 patients we had histopathological data of 44 patients. Considering histopathology data as standard, comparing the results of USG and FNAC with the same, we found that Sensitivity of USG was 92% whereas that of FNAC was 92%. In study of Lokhande et al sensitivity of USG was 71.43% and of FNAC is 75%. So, these results are much lower than present study²¹. From our results we recommend USG should be first step in diagnosis of suspected thyroid nodule. National Comprehensive Cancer Network (NCCN) suggests all thyroid nodules be evaluated with thyrotropin and USG of thyroid and neck as a first step and prefers FNA (with or without sono-guidance) as an investigation of choice in only suspicious lesions²².

 

CONCLUSION

Ultrasound evaluation is non-invasive, readily available, relatively inexpensive and with good resolution it helps to detect non-palpable and clinically silent nodules. USG also guides for fine needle aspiration of suspicious nodules. USG-thyroid should be considered as a first step and as an investigation of choice in evaluation of thyroid nodule.

 

REFERENCES