Thyroid Scintigraphy in the Era of Fine-Needle Aspiration Cytology

Ilenia Pirola; Elena Di Lodovico; Claudio Casella; Letizia Pezzaioli; Paolo Facondo; Alberto Ferlin; Davide Lombardi; Carlo Cappelli

Disclosures

Clin Endocrinol. 2021;94(4):711-716. 

In This Article

Abstract and Introduction

Abstract

Purpose: To evaluate whether thyroid scintigraphy would alter the clinical management of patients referred for fine-needle aspiration cytology (FNA).

Methods: We reviewed the medical and imaging records of patients referred to our Department between 2016 and 2019. All the patients had to take a serum thyrotropin test administered in our hospital at least two months before the FNA; where the TSH level was ≤1.5 mIU/L, the patients were subjected to a scan and subsequently to FNA, where indicated. We selected only healthy patients with no previous history of thyroid disease, who were not taking any drugs and who had a TSH level of ≤1.5 mIU/L. We excluded patients with multinodular goitre.

Results: A total of 176 patients were analysed. A total of 67/176 patients (38%) showed a serum of TSH ≤ 0.27 mIU/L. Scintigraphy identified a hot nodule in 142 lesions (80.7%), a warm nodule in 8 lesions (4.5%) and a cold nodule in 26 lesions (14.8%). The ROC curve analysis indicated that a TSH value of ≤0.42 mIU/L identified patients with hyperfunctioning nodules with a sensitivity of 65% and a specificity of 77%. All patients with cold and warm nodules were submitted to FNA: 22/26 (85%) and 5/8 (63%) lesions showed suspected malignancy or were compatible with malignancy, respectively.

Conclusion: Speculating on our data, if we had subjected our patients to FNA as indicated by the 2015 ATA guidelines, we would have subjected 117 patients to cytology, from whom 83 had undetected hot nodules. Conversely, by adopting scintigraphy for all patients with TSH ≤ 1.5 mIU/L, 109 patients have avoided FNA. However, our study was performed in a region with a history of mild iodine deficiency. Therefore, we cannot claim that our observation is valid for patients born and living in areas with sufficient iodine uptake. We recommend thyroid scintigraphy for treating single thyroid nodules in euthyroid patients born and living in regions with an iodine deficiency, when TSH levels are below 1.5 mIU/L before FNA.

Introduction

Thyroid nodules are a common issue in clinical practice.[1] In the Framingham survey, clinically apparent thyroid nodules were found in 6.4% of women and 1.5% of men.[2] These figures significantly underestimate the true frequency of this disorder, as highlighted by non-selective surveys using ultrasonography, in which 20%–76% of women had at least one thyroid nodule.[3–5] The clinical significance of these surveys is primarily the need to exclude thyroid cancer, which accounts for 4%–6.5% of all thyroid nodules.[6–8]

Fine-needle aspiration cytology (FNA) is the most accurate examination for ruling out thyroid cancer today. Moreover, FNA is safe, well accepted by patients, cost-effective and can be performed in an outpatient setting.[9] However, FNA should almost always be avoided in patients with autonomously functioning thyroid nodules (AFTNs) for two main reasons: firstly, despite few case reports showing malignancy in these nodules, they have a very low risk of cancer; secondly, there is the risk of obtaining equivocal results, such as indeterminate follicular lesions, which are likely to require surgery.[10,11]

Thyroid scintigraphy is the only technique that determines the functional status of a nodule. Authoritative guidelines by the American Thyroid Association (ATA), American Association of Clinical Endocrinologists (AACE), American College of Endocrinology (ACE) and the Associazione Medici Endocrinologi (AME)—AACE/ACE/AME Task force of thyroid nodules—recommend scintigraphy in patients with thyroid nodules only if the serum thyrotropin (thyroid-stimulating hormone or TSH) is undetectable or below the lower reference limit. In addition, a thyroid scan may also be considered in multinodular glands to detect functional autonomy, which is most common in iodine-deficient areas.[11,12] Indeed, the prevalence of AFTNs with normal TSH does not prove negligible.[13–15]

Therefore, it is reasonable to deduce that the absence of thyroid scintigraphy in treating a patient with a thyroid nodule and a normal TSH level can lead to undetected AFTNs being subjected to FNA.

In addition, a previous personal observation showed a significant number of patients with AFTNs among those with serum TSH ≤ 1.5 mIU/L.

The aim of this study was to evaluate whether thyroid scintigraphy would alter the clinical management of patients referred for FNA.

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