Study of ultrasonography of thyroid nodules and its correlation with FNAC

 

 

Abstract               Background: Thyroid nodules occur with relatively high frequency in the general population and have various etiologies. Ultrasound of the neck is a simple method to have preliminary information about the gland which can be confirmed by fine needle aspiration cytology. In the present study, we have attempted to correlate the findings of ultrasound of thyroid with the FNAC findings. Aim of the study: To study the ultrasonography of thyroid nodules and its correlation with fine needle aspiration cytology. Materials and Methods: The present study was done over a period of two years and 160 cases of enlarged thyroid were studied by ultrasound examination of the gland followed by fine needle aspiration cytology in all the cases. Patient demographics, the US findings, echogenicity, vascularity etc were noted. Results: In the present study a total of 160 cases were included. The patient age ranged from 10 years to more than 50 years. The male to female ratio was 1:2.2. On ultrasound examination of the neck 145/160 (90.6%) were reported as benign, 15/160 (9.3%) were reported as malignant. Majority of the patients were among 30-40 years with a female preponderance. On FNAC a total of 147/160 (91.8%) were diagnosed as benign lesions and 13/160 (8.1%) were reported as malignancy. On ultrasound, two cases were reported as false positives for malignancy. Conclusion: Thyroid nodules or lesions are frequent clinical complaint in the general population and it is more common in middle-aged females. Benign lesions are more common as compared to thyroid malignancies. Regular margins, solid internal composition of the nodule, no calcification, ‘not-taller-than wider’ lesions and presence of peripheral halo favor benign nature of the thyroid lesions. There is good correlation between thyroid ultrasound and FNAC findings.

Key Words: USG of thyroid, thyroid nodule, FNAC of thyroid.

 

 

INTRODUCTION

Thyroid nodules occur with relatively high frequency in the general population with prevalence of 4%–7% by palpation alone and 13%–67% by sonographic evaluation.^1,2 However, less than 7% of the thyroid nodules are malignant.^3,4 Imaging modality of choice for the investigation of thyroid nodules is high resolution ultrasound (HRUS). Ultrasonography is the modality of choice for initial characterization of a thyroid nodule.⁵ Ultrasonography gives good graphic representation of regional anatomy, has high resolution, it is less expensive, it is simple test, and it depicts the internal structure of the thyroid gland and the regional anatomy and pathology without using ionizing radiation or iodine containing contrast medium. ^{6, 7} It is used to define the nature of the lesion, whether solid or cystic; to differentiate thyroid from extra thyroidal masses, assessment of blood flow pattern in and around the lesion, to differentiate between benign and malignant thyroid nodules, to ascertain invasion in nearby structures and to identify additional nodular lesions or enlarged lymph nodes. ^{8, 9} During the past two decades, the widespread use of ultrasonography (US) for evaluation of thyroid and neck disease has resulted in a dramatic increase in the prevalence of clinically unapparent thyroid nodules, estimated at 20% to 76% in the general population. Moreover, 20% to 48% of patients with a single palpable thyroid nodule are found to have additional nodules when investigated by ultrasound. ^{10, 11} The growth of nodules can lead to a multinodular goitre. The clinical importance of thyroid nodules is that when very large, they can sometimes cause local compressive symptoms or may result in a hyperfunctioning gland. It is of utmost importance to exclude the presence of any malignant lesion in the thyroid, which accounts for about 5% of all thyroid nodules, independent of their size. ^{12, 13} Fine Needle Aspiration Cytology (FNAC) is the investigation of choice in discrete thyroid swellings. FNAC has excellent patient compliance, is simple and quick to perform in the outpatient department and can be readily repeated. Ultrasound maybe used to guide the needle for more accurate sampling. An US guided FNAC procedure may be done especially when the thyroid enlargement is not very apparent or in cases of smaller lesions. ¹⁴

 

MATERIALS AND METHODS

Permission from institutional ethical committee was taken. Informed consent was taken from all patients who were willing to participate in the study. This was a prospective hospital based study, done in the department of Radiodiagnosis at Shri Sathya Sai Medical College and Research Institute, Kancheepuram, Tamil Nadu, India. The study was done over a period of two years from January 2017 to January 2019. A total of 160 cases were studied. Patients presenting with thyroid nodules attending out-patient departments (OPD) of General Surgery, ENT and General Medicine were referred for ultrasound examination of the neck. All the patients were evaluated by thorough clinical examination. Ultrasound of thyroid was done in our department in all cases using high-frequency linear array Ultrasound transducer. Equipment: In the present study, gray-scale real-time ultrasound examination was done using 7.5 MHz linear array transducer.

Technique of Examination: The patient was examined in the supine position with an extended neck. A pillow was placed under the shoulders to provide better exposure of the neck. Since the gland is situated superficially, 7.5 MHz linear array transducer was used. The entire thyroid gland from upper to the lower pole and the isthmus was examined in the longitudinal and transverse planes. Bilateral carotid arteries, jugular veins, and supraclavicular fossa were also examined. The FNAC procedure was explained to the patient and the patients were asked not to swallow and not to move during the procedure. FNAC thyroid was done in all 160 cases under aseptic precautions. FNAC was performed with 23G needle. The material collected was smeared onto glass slides and was fixed in isopropyl alcohol. Some slides were air dried. Later in the department of Pathology, these slides were stained with Hematoxylin and Eosin stains (HandE), Giemsa stain and were reported. The cytology reports were correlated with the USG findings.

Inclusion Criteria:

• Patients willing to participate
• Age group from 10 years to 50 years
• Both genders
• All the patients with thyroid nodule detected on ultrasound

Exclusion Criteria:

• Patients not willing to participate
• Age group less than10 years
• Patients in whom only ultrasound was done without FNAC, were excluded

 

OBSERVATIONS AND RESULTS

Sample size: In the present study a total of 160 cases were included. On ultrasound neck, of the 160 thyroid nodules examined, 145/160 (90.6%) were reported as benign, 15/160 (9.3%) were reported as malignant. On FNAC a total of 147/160 (91.8%) were diagnosed as benign lesions and 13/160 (8.1%) were reported as malignancy.

Table 1: Age-wise distribution of the cases

In the present study, age group distribution included was from 10 years to more than 50 years. Majority of the patients, ie 46.8% (75/160) were among 30-40 years. Next common was among 20-30 years ie, 21.8% (35/160)

 

Table 2: Gender-wise distribution of the cases

In the present study, majority of the patients were females 68.7% (110/160) compared to males 31.2% (50/160) and the male to female ratio was 1:2.2. In the present study majority of the cases (120/160), 75% presented as solitary nodule and (40/160) 25% cases presented as multiple nodules.

 

 

 

Table 3: Ultrasound findings of the cases

On ultrasound neck of the 160 thyroid nodules, 145/160 (90.6%) were reported as benign, and 15/160 (9.3%) were reported as malignant lesions. Of the benign lesions, 130 (89.6%) had well defined margins, in 127 (87.5%) had solid internal composition/nodules. Calcification was absent in 130 (89.6%) cases. Hypoechogenicity was seen in 20(1.3%) nodules. More cases were hyperechoic and isoechoic.

Figure 1                                                           Figure 2

Figure 1: HRUS shows enlarged thyroid with altered echogenicity suggestive of Goitre; Figure 2: Isoechoic thyroid nodule with peripheral hypoechoic rim

 

Table 4: FNAC diagnosis of the cases

In the present study, on FNAC a total of 147/160 cases (91.8%) were diagnosed as benign lesions and 13 (8.1%) were reported as malignancy. Majority were reported as adenomatous goiter i.e., 61.2% (98/160) followed by colloid nodule i.e. 20.6%.

 

Table 5: Comparison between USG findings and FNAC

 

DISCUSSION

Sample size: In the present study a total of 160 cases were included. Hassan et al ¹⁵ Studied 66 patients in a similar study and Gupta DK et al ¹⁶ had 100 similar patients as study population.

Age distribution: In the present study, age group distribution included from 10 years to more than 50 years. Majority of the patients, i.e. 46.8% (75/160) were among 30-40 years. Next common age group was among 20-30 years i.e., 21.8% (35/160). Hassan et al ¹⁵ observed in their study of 66 patients, that the age of patients ranged between 10-69 years. The mean age was 39 years and the maximum number of patients affected belonged to the age group of 30 to 39 years (36.4%). Gupta DK et al ¹⁶ also observed that of the 100 patients, maximum patients (35%) were found to be in the age group of 41-60 years. In the study by Chakraborty S et al ¹⁷ maximum number of cases fell in the age group of 31-40 years (n=35) followed by 21-30 years age group (n= 24). The youngest patient was 14 years old and oldest was 70 years old. Bayewu et al ¹⁸ in a similar study also reported the age from 22 to 71 years with a mean of 44.05 ± 11.79 years. Gender distribution: In the present study, majority of the patients were females 68.7% (110/160) compared to males 31.2% (50/160) and the male to female ratio was 1:2.2. In the study by Hassan et al¹⁵ of the 66 patients included, 13 were male (19.7%), and 53 were females (80.3%) and the male to female ratio was 1:4. Gupta DK et al ¹⁶ observed that out of the 100 patients that were reviewed 74 were females (74%) and 26 were males (26%) and the male to female ratio was 1:2.8. Chakraborty S et al¹⁷ observed that out of the 100 cases in their study, 23 (23.0%) were male and 77 (77.0%) were female and the male to female ratio was 1:3.3. Females (77.0%) were more commonly affected than males (23.0%).

In the study by Bayewu et al ¹⁸ of the 110 cases obtained, 103 were females and 7 were males with a male to female ratio of 1:14.7. Our findings compare well with the observations of the above authors. USG findings: In the present study, on ultrasound neck of the 160 thyroid nodules examined, 145/160 (90.6%) were reported as benign, 15/160 (9.3%) were reported as malignant. Among benign cases 130 (89.6%) had well defined margin, 127 (87.5%) had solid internal composition, 20 (1.3%) nodules were hypoechoic, 60(41.3%) nodules were hyperechoic, 130(89.6%) of the benign nodules were well defined with thin peripheral continuous halo. We also had 130 (89.6%) lesions that were ‘Not taller than wider’. Among reported as malignancy 9 (60%) had poorly defined margins, 10 (66.6%) were solid nodules, and 15(100%) nodules were hypoechoic. In a similar study done by Kapali et al¹⁹ 51% (29 nodules) were hypoechoic, 49% (28 nodules) were hyperechoic. Central vascularity was present in 68.4% (39) patients and no significant central vascularity was seen in 31.5% (18) patients. Cystic areas were identified in 23% patients, two patients had honeycombing and 56.1% (32) patients had no cystic areas. In the study by Bayewu et al¹⁸ most of the nodules 103 (93.6%) were wider than tall, isoechoic were 59 (53.6%), mostly spongiform 83 (75.5%), mostly well-defined 101 (91.8%) with thin surrounding halo in 93 (92.1%) cases.

Calcifications: In the present study, among benign cases there was no calcification seen in 130 (89.6%) cases. Macro calcification was seen in 15 (10.3%) patients. Among malignancy 11 (73.3%) showed micro calcification, and 4 (26.6%) showed no calcification. Kapali et al ¹⁹ reported no calcification being identified in 54.3% (31 patients), macro calcification in 26.3% (15 patients), micro calcification in 17.5% (10 patients) and one patient (1.7%) had mixed macro calcification and micro calcification. Bayewu et al ¹⁸ in their study observed that calcification was present in 18 (16.4%) patients, of which 5 (27.8%) were macrocalcifications while 13 (72.2%) were microcalcifications. Color flow was present in 84 (76.4%) nodules, of which 76 (69.1%) were peripheral while intranodal were 8 (7.3%).

 

 

FNAC results

In the present study, on FNAC a total of 147/160 cases (91.8%) were diagnosed as benign lesions and 13 (8.1%) were reported as malignancy. Majority were cytologically reported as adenomatous goiter i.e., 61.2% (98/160) followed by colloid nodule in 20.6% (33/160). Also 6.8% (11/160) were reported as Follicular neoplasm, 3.7% (6/160) as Acute thyroiditis and 6.2% as Autoimmune thyroiditis (10/160). Hassan et al ¹⁵ observed in their 66 patients, only 6 patients (9%) had thyroid carcinoma while 56 patients (84.84%) had benign pathological results and 4 patients (6.16%) had suspicious pathological results. Regarding the malignant thyroid nodules, the prevalence was highest in age group of 50-59 years (50%). Five patients of thyroid carcinoma (83.3%) had solitary nodule more than 10 mm in largest dimension and only one patient (16.7%) had multiple thyroid nodules. Chakraborty S et al ¹⁷ in their study of 100 cases observed that 80 were benign and 20 were malignant on FNAC. As per gender, 9 (39.1%) out of 23 male patients had malignancy and 11(14.3%) out of 77 female patients had malignancy. Males had higher malignancy rates than females. Bayewu et al¹⁸ in their study reported that on cytological evaluation, 101 lesions were benign (91.8%) and 9 were malignant (8.2%).

Kapali et al ¹⁹ reported a spectrum of thyroid llesions like normal thyroid background was present in 67% (38 patients); colloid/ adenomatous hyperplasia changes were seen in 29.8% (17 patients), and Hashimoto’s thyroiditis in two patients. Our observations correspond to those of the above authors.

Clinical presentation

In the present study majority of the cases (120/160), 75% presented as solitary nodule and (40/160) 25% cases presented as multiple nodules. Chakraborty S et al ¹⁷ observed that out of the total 100 patients evaluated, 44 (44.0%) patients had solitary thyroid nodule as compared to 56 (56.0%) patients who had multinodular goitre. Gupta DK et al ¹⁶ also observed that out of their 100 patients, palpation and clinical examination demonstrated 11 cases of multiple nodules.

 

CONCLUSION

Thyroid nodules or lesions are frequent clinical complaint in the general population and it is more common in middle-aged females. Benign lesions are more common as compared to thyroid malignancies. Regular margins, solid internal composition of the nodule, no calcification, ‘not-taller-than wider’ lesions and presence of peripheral halo favor benign nature of the thyroid lesions. There is good correlation between thyroid ultrasound and FNAC findings.

 

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