Sonographic Presentation of Metastases to the Thyroid Gland

A Case Series

Rosa Falcone; Valeria Ramundo; Livia Lamartina; Valeria Ascoli; Daniela Bosco; Cira Di Gioia; Teresa Montesano; Marco Biffoni; Marco Bononi; Laura Giacomelli; Antonio Minni; Maria Segni; Marianna Maranghi; Vito Cantisani; Cosimo Durante; Giorgio Grani

Disclosures

J Endo Soc. 2018;2(8):855-859. 

In This Article

Abstract and Introduction

Abstract

Incidental sonographic discovery of thyroid nodules is an increasingly common event. The vast majority is benign, and those that are malignant, are generally associated with an indolent course and low mortality. Sonographic scoring systems have been developed to help clinicians identify nodules that warrant prompt fine-needle aspiration cytology (FNAC), but they are based largely on experience with papillary thyroid cancers. We analyzed the performance of four scoring systems widely used for this purpose (American Thyroid Association Guidelines, American Association of Clinical Endocrinologists/American College of Endocrinology/Associazione Medici Endocrinologi Guidelines, European Thyroid Imaging Reporting and Data System, and Korean Thyroid Imaging Reporting and Data System) in patients whose nodules proved to be metastases from other solid cancers. Such nodules reportedly account for 0.2% to 3% of all thyroid malignancies. Each scoring system was used to assess retrospectively the malignancy risk and indications for FNAC of five patients' thyroid nodules that were ultimately diagnosed as metastases (from renal cell carcinoma, breast cancer, and lung cancer in two cases and esophageal cancer). The primaries identified in these cases are those most commonly reported to metastasize to the thyroid. In two cases, the thyroid metastases were the first sign of undetected neoplastic disease. Although sonography alone cannot distinguish thyroid metastases from primary thyroid malignancies, all four scoring systems classified the metastatic nodules as suspicious enough to require FNAC. The five cases accounted for 0.2% of those cytologically examined in our center. In most cases, cytology provided useful guidance for the subsequent management of these lesions, which differs from that of primary thyroid cancers and requires multidisciplinary input.

Introduction

Detection of asymptomatic thyroid nodules during ultrasound screening programs or imaging performed for other indications is increasingly common, and the clinical management of these lesions is a challenge. Because most nodules are benign, it is important to avoid overdiagnosis and overtreatment. Clinical practice guidelines recommend restriction of fine-needle aspiration cytology (FNAC) to selected lesions whose ultrasonographic features are associated with malignancy. Several scoring systems have been developed for this purpose.[1–4] The "suspicious" features considered vary from system to system, but most (e.g., marked hypoechogenicity, irregular margins, microcalcifications) have been selected on the basis of studies of papillary thyroid cancers. Some of the systems have also been found to perform well in the detection of medullary thyroid cancer,[5] but they are less accurate in patients with follicular thyroid cancers.[6]

What about the 0.2% to 3.0% of thyroid malignancies that ultimately prove to be metastases from other solid tumors[7,8]? Thyroid metastases have been reported in several types of cancer, the most common being renal-cell, lung, breast,[9] and colon carcinomas.[10] Despite their rarity, these entities must be considered during the workup of new thyroid nodules. No data are available on the performance of ultrasound risk-assessment systems in patients whose thyroid nodules are metastatic. To address this gap, we reanalyzed five cases of thyroid metastases that were referred to our unit for assessment of thyroid nodules, retrospectively calculating the indication for FNAC using four of the ultrasound-based systems most widely used for this purpose (Table 1).

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