Abstract
Purpose : To evaluate retrospectively the safety, yield and diagnostic potential of ultrasonography (US)-guided fine-needle aspiration cytological analysis of thyroid gland lesions.

Material and Methods : We retrospectively evaluated the results of 50 fine-needle aspiration cytological analysis (FNAC) of different thyroid lesions in 50 patients (Median age, 47 yrs; age range, 14-78 yrs). Fine-needle aspiration cytological analysis was performed as an outpatient procedure with direct ultrasound guidance using 21-23 gauge fine-needles and samples were put in storage solution. Hospital records were reviewed 6 months-to 1 year following FNAC to determine diagnosis, delayed complications and influence of biopsy findings on subsequent patient treatment.

Results : Fortyfive (90%) specimens were adequate for cytological diagnosis. Eight (16%) cases were diagnosed as neoplastic (Malignant and benign) out of which one case was diagnosed as malignant and was confirmed as follicular cell carcinoma following thyroidectomy. Patients who were diagnosed as neoplastic underwent surgical resection biopsy confirmation. Forty (88.8%) of the patients after ultrasonography guided fine-needle aspiration were treated conservatively and no evidence of missed tumour manifested during the follow up period of this group.

Conclusion : US-guided fine-needle aspiration cytology is a safe and less expensive outpatient procedure with a high diagnostic yield and accuracy with wide dynamic range in acquiring the samples and it obviates the need for core needle sampling/excision biopsy for majority of the thyroid lesions.

Introduction
Fine-needle aspiration cytological analysis is widely considered the diagnostic technique of choice in the assessment of thyroid lesions. FNAC analysis is minimally invasive, safe and usually performed as an outpatient procedure. The accuracy of the FNAC analysis approaches 95% in the differentiation of benign from malignant nodules of the thyroid gland¹ and diagnostic retrieval rate reaches up to 87%.² In our institution, patients with goitres are initially examined biochemically followed by US examination and guided FNAC analysis.

Material and Methods

Patients and procedures
Retrospective study was performed of all patients who underwent US-guided fine-needle aspiration cytological analysis of thyroid lesions over a period of 1 year.
In all cases, a comprehensive preliminary US evaluation of the neck and thyroid including colour Doppler studies was performed by using a 7.5-10 MHz linear array transducer. The FNAC were performed by experienced radiologists. The procedure was generally performed without local anaesthesia. Coagulation screening was not routinely performed unless there was pre existing risk of bleeding. 23 gauge needles were used in all patients. The aspiration was directed towards the solid lesions, solid element of a partially solid and cystic lesion and wall of a predominantly cystic lesions and randomly performed in patients with diffuse disease where indicated. The number of passes was decided by the operator, usually two passes per lesion sampled. A review scan was performed in all patients after the procedure to rule out any complication. The procedure was generally well tolerated with no significant complication.

Cytological Analysis
The aspirate was kept in media storage solution and examined by experienced cytopathologists. Sample adequacy was assessed as a subjective judgement by the cytopathologists at the time of analysis.

Data collection
At the time of FNAC, lesion size, echo pattern, doppler characteristics and number of lesions were recorded together with the details of the site, needle gauge, number of passes and any immediate complications.
Patient’s hospital records were reviewed over a period of 6 months to 1 year after the FNAC to determine final diagnosis and influence of results on subsequent patient treatment. Final diagnosis in all patients was determined with the results of surgical resection or with FNAC findings, with subsequent clinical follow-up.

Results
Clinical data : The study included 50 fine-needle aspiration cytological analysis. Patients ranged in age from 14 to 74 year (median age, 47 yrs); 39 (78%) patients were females and 11 (22%) were males.

All patients were referred for biopsy from either the endocrinologic or general surgical services and in all patients a cytological diagnosis was considered necessary to assist in further management.

Lesions on which FNAC was performed included 32 (64%) solid lesions, 10 (20%) partially solid and partially cystic lesions, 4 (8%) cystic lesions, and 4 (8%) diffuse enlargement of the thyroid gland.

Sample adequacy

Table : Cytologic diagnosis in 50 FNAC samples
Diagnosis	No. of Biopsies
Inadequate sample	5
Normal thyroid tissue	1
Non neoplastic (colloid nodule or Follicular hyperplasia)	36
Neoplastic-benign lesion	7
Neoplastic-malignant lesion	1

Forty five (90%) samples were considered adequate for cytological diagnosis by the reporting cytopathologist who was not present during the FNAC procedure.

Out of the seven benign neoplastic lesions diagnosed by FNAC, four cases were confirmed as benign by surgical resection of the thyroid for other therapeutic reasons. The other three cases underwent regular follow up and showed clinical features of benign lesion.

The case diagnosed as malignant by FNAC was confirmed as follicular carcinoma following surgical resection.

Discussion
Clinical history and examination are frequently non-specific in the characterization of masses of the thyroid gland.³ Though the incidence of thyroid malignancy is less than 50 per million population⁴ timely diagnosis are important as surgical treatment of local disease can be curative.

Radiological imaging in the form of scintigraphy, computed tomography, magnetic resonance imaging and US plays an important role in the staging of known cancer of the thyroid gland.⁵ However accurate tissue characterisation is not possible by using current imaging studies and cytological analysis is usually undertaken. Although US is a very effective first line investigation in delineating thyroid masses, its role is primarily that of differentiating solid from cystic lesions and confirming whether nodules are solitary or multiple.

Fine-needle aspiration cytology (FNAC) is widely accepted as the most accurate, sensitive, specific and cost-effective diagnostic procedure in the assessment of thyroid nodules and helps to select people preoperatively for surgery.⁶ The efficacy of fine-needle aspiration (FNA) biopsy and its role in the management of a nodular goitre are clearly established. The accuracy of cytological diagnosis approaches 95% in the differentiation of benign from malignant nodules of the thyroid gland.1 With adequate sampling, the finding of 100% sensitivity in the diagnosis of malignant neoplasms by FNAC reaffirms its role as the procedure of choice in the initial screening of thyroid nodules.⁷

FNAC can specify the nature of focal lesion with high sensitivity, specificity and diagnostic accuracy in the cases of non-follicular lesions. Histological evaluation is required to specify the nature of the lesion in cases where cytology is indicative of the presence of follicular proliferation,⁸ as cytology alone may not be enough to differentiate between follicular adenoma and carcinoma.

The introduction of ultrasonography permits higher diagnostic accuracy of the evaluation process. This is achieved not only by reducing false negative reports but, more important, by decreasing false positive results.⁹

FNAC analysis of the thyroid gland benefits from being safe and accurate, and the needles used for FNAC analysis are less expensive than the disposable needles used for core-needle biopsy. Fine-needle aspiration cytological analysis is a safe, minimally invasive, less expensive outpatient procedure with an accuracy approaching 95% in the differentiation of benign from malignant lesion if it is carried out by technically skilled clinician. Though it provides inadequate samples in 10-12% of cases, this procedure can be repeated as many times as necessary due to its minimal invasiveness and very low morbidity.²

The combined use of US-guided FNAC with evaluation of the sample at the bedside by a cytopathologist has been proposed to optimise diagnostic yield and accuracy.¹⁰ However, this dual-operator approach has manpower, time, and cost implications.

In our institution, the results audited show a very low incidence of repeatedly insufficient or non diagnostic FNAC procedures and no incidence of recorded complications, US-guided FNAC analysis remain the screening tool of choice in the assessment of thyroid lesions.

Conclusion
US-guided fine-needle aspiration cytological analysis is a safe, minimally invasive, less expensive outpatient procedure and should be the procedure of choice in the initial screening of thyroid lesions.

References

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