Thyroid disease in the pediatric patient: emphasizing imaging with sonography

Ultrasound findings of the thyroid gland in children and adolescents

Ultrasonography (US) is an important diagnostic tool in evaluating thyroid diseases in pediatric patients. This pictorial essay reviews the application of various ultrasound techniques such as B-Mode ultrasound and color Doppler, elastography and contrast enhanced ultrasound (CEUS) in children and adolescents in various thyroid pathologies including congenital thyroid abnormalities, diffuse thyroid diseases (DTD), focal thyroid lesions and thyroid malignancy.

Intrathyroidal Ectopic Thymus and Sonoelastographic Findings

BACKGROUND

Intrathyroidal ectopic thymus (IET) can be misdiagnosed as thyroid nodules.

PURPOSE

To evaluate the sonoelastographic findings of IET in pediatric population.

METHODS

Twelve children who had been examined with ultrasound (US) and strain elastography between December 2012 and December 2019 were included in this retrospective study. The patients' demographics and ultrasonographic findings including the location, margin, shape, diameters, volume, structure, vascularity, and elastography values of the lesions were evaluated.

RESULTS

Twelve lesions were detected in 12 asymptomatic patients (3 females and 9 males) with a mean age of 4.67 ± 2.27 years. The most common location of the IET was in posterior part and middle third of thyroid, and the most common appearance on US was a well-defined, ovoid-shaped, and predominantly hypoechoic solid lesion with punctate/linear branching hyperechogenities. The lesions were mostly hypovascular on Doppler US. The mean strain ratio on elastography was found to be 1.10 ± 0.04. In the follow-up of 7 patients with available information, there was not any significant change in size or appearance of IET on US.

CONCLUSION

IET should be considered in the differential diagnosis of the lesions within the thyroid. The first step to accurately diagnose an IET is to consider it in the differential diagnosis. In addition to US, strain elastography findings can be used to distinguish IETs from papillary thyroid cancers which can have similar US appearance, and help avoid unnecessary biopsies.

Pediatric thyroid ultrasound: a radiologist's checklist

Ultrasonography (US) is the imaging method of choice for evaluating the pediatric thyroid gland, complemented by scintigraphy and thyroid function tests, especially when evaluating children with suspected congenital hypothyroidism, goiter, infectious or autoimmune diseases, or neoplasm. Diagnostic considerations in newborns with congenital hypothyroidism mainly include dysgenesis, dyshormonogenesis, transient hypothyroidism and central (hypophyseal) hypothyroidism. The midline of the neck should be scrutinized for thyroid tissue from the floor of the mouth to the thoracic inlet. Cystic and echogenic ultimobranchial remnants should not be misinterpreted as orthotopic thyroid tissue. Diffuse thyroid diseases affect older children; these comprise Hashimoto and Graves diseases and infectious thyroiditis and exhibit features similar to those in adults. It is important to note that the diffuse sclerosing variant of papillary thyroid cancer can complicate thyroiditis and should not be confused with Hashimoto disease. In children with solid nodules the threshold for fine-needle aspiration biopsy or surgery should be lower compared to adults because of a higher likelihood of malignancy compared with adults. Biopsy should be considered in nodules with suspicious ultrasonographic features, even when smaller than 1 cm. Adult classification systems of thyroid nodules, although useful, are not sufficient to safely discriminate the nodules' likelihood of malignancy in children. We describe key sonographic findings and suggest a standard checklist that might be considered while performing and interpreting thyroid US in neonates and children.

Intrathyroidal ectopic thymus tissue: a diagnostic challenge

OBJECTIVES

The prevalence of thyroid nodules in pediatric population is 0.2-2%, which is lower than adults. However, the probability of the nodule to be malignant is higher than adults (20-73%). Differential diagnosis of thyroid lesions in children includes intrathyroidal ectopic thymus tissue (ITT). ITT can present as a thyroid nodule, and be confused with malignancy with its hyperechoic pattern; this might cause unnecessary fine-needle aspiration biopsies and/or surgical interventions. In the current study, we mainly aim to define both US and color Doppler ultrasonography (CDUS) characteristics of ITT. We also aim to describe the most sensitive and most specific diagnostic parameters of ITT.

METHODS

We have evaluated US examination reports of 56 children for whom differential diagnosis included ITT between February 2015 and August 2018. We have recorded sonographic characteristics of the lesions, CDUS data, and thyroid hormone levels.

RESULTS

Study population consists of 56 patients (22 ITT, 34 other diagnoses). Median age of the population is 10 years. Age, sex, laboratory results, and follow-up change in lesion diameters do not show any significant difference between ITT and other diagnosis groups. Typical US appearance, fusiform lesion shape, and isovascular CDUS characteristics are higher in ITT group. The median value of the lesion's highest diameter is smaller in ITT group. The most valuable criteria to predict ITT presence were the fusiform shape and the longest diameter of the lesion.

CONCLUSIONS

Fusiform shape and a maximum diameter of ≤ 9 mm are the most selective criteria to predict ITT diagnosis.

Ectopic thyroid tissue presenting as a new neck mass in a pediatric patient

Ectopic thyroid tissue is an uncommon, but well-documented condition. We present a case of an ectopic thyroid gland with an atypical presentation as a new neck mass in a 3-year-old female without symptoms of hypothyroidism. Imaging confirmed ectopic thyroid and suggested thyroiditis due to hyperemia and heterogeneity on ultrasound. However, there were no laboratory findings of hypothyroidism. An understanding of anatomy and sonographic features of ectopic thyroid gland allows the radiologist to provide a more accurate differential diagnosis in the setting of a neck mass.

Ultrasound and the Evaluation of Pediatric Thyroid Malignancy: Current Recommendations for Diagnosis and Follow-up

Ultrasound (US) plays a critical role in the evaluation, treatment, screening, and surveillance of thyroid malignancy in pediatric patients. This review aims to summarize recent advances in this topic. Improvements in imaging technology have amplified the advantage of US and US-guided fine-needle aspiration biopsy for thyroid nodule evaluation, cancer diagnosis, and surgical planning. Ultrasound has a definitive screening role for early cancer detection in high-risk patients, including those with a history of radiation exposure from childhood treatments, environmental radiation disasters, or hereditary/familial cancer syndromes. Finally, US is a key component of lifelong surveillance for recurrence among pediatric thyroid cancer survivors.

Intrathyroidal thymic tissue in children: Avoiding unnecessary surgery

BACKGROUND/PURPOSE

Intrathyroidal thymic tissue may be misinterpreted as a thyroid lesion in children, leading to invasive tests or resection. We sought to describe the characteristic imaging features of these lesions and to evaluate the safety of non-operative management.

METHODS

A retrospective review of all patients less than 18years old with intrathyroidal thymic tissue from 2000 to 2016 was performed. Data collection included patient demographics, imaging results, interventions, and outcomes.

RESULTS

Eleven patients were identified using institutional radiology and pathology databases. Median patient age and lesion size at presentation were 5years old (range 2 to 8years old) and 0.9cm (range 0.4 to 9.2cm), respectively. Six lesions were incidentally identified, six were left-sided, and the most common location was the lower pole. Ultrasonographic features were reproducible and included well demarcated (10/11), hypoechoic lesions (11/11), containing punctate/linear internal echoes (11/11), and occasional mild hypervascularity (6/11). All cases demonstrated interval size and echotexture stability over a median surveillance period of 3years (range 1 to 8years). While 9 patients were simply observed, the first patient in this series underwent excision, while another had a fine needle aspiration to confirm pathology.

LEVEL OF EVIDENCE

Study of diagnostic test, Level IV.

CONCLUSION

Intrathyroidal thymic tissue has typical clinical and sonographic characteristics which allow for appropriate diagnosis and avoids thyroid resection.

Ultrasound Measurements of Thyroid Gland Volume at 36 Weeks' Corrected Gestational Age in Extremely Preterm Infants Born before 28 Weeks' Gestation

BACKGROUND

Thyroid ultrasound is a non-invasive imaging tool and provides good evaluation of thyroid anatomy, location, vascularisation, and echogenicity. The aim of this study was to assess thyroid function and thyroid volume in extremely preterm infants born before 28 weeks' gestation evaluated at 36 weeks' corrected gestational age (CGA) compared to term infants' normative data in the literature.

DESIGN

In this largest prospective UK study of extremely premature infants born at less than 28 weeks' gestation, thyroid volume measurement was assessed at 36 weeks' CGA. Fifty-five extremely preterm infants (28 males) who were born before 28 weeks' gestation were recruited to the study. All infants had ultrasound assessment of the thyroid gland at 36 weeks' CGA. We also prospectively measured thyroid stimulating hormone (TSH) and free thyroxine (FT4) in all infants at the time of recruitment (within 5 days of birth), at days 14, 21, and 28, and at 36 weeks' CGA.

RESULTS

The mean thyroid volume was measured at 0.57 mL (SD ±0.18). There was no association between mean thyroid volume and thyroid function (TSH or FT4). No associations were found between mean thyroid volume and gestation or birth weight in these infants.

CONCLUSIONS

Our findings provide a reference range with a mean thyroid volume of 0.57 mL (SD ±0.18) in this extremely preterm age group if less than 28 weeks' gestation. Thyroid volume at birth can vary from country to country due to variations in iodine intake as well as gestational age.

Thyroid Imaging in Infants

Congenital hypothyroidism is the most common preventable cause of mental retardation. It is important to know the cause of each patient's thyroid dysfunction to foresee the course of therapy and outcomes. Imaging methods, such as ultrasound and thyroid scan, help determine the anatomy and function of the thyroid gland. Although thyroid scan is considered superior in detecting ectopic thyroid tissue, ultrasound is able to detect the presence of thyroid tissue not otherwise visualized in 15% of patients.

The Diffuse Sclerosing Variant of Papillary Thyroid Cancer Presenting as Innumerable Diffuse Microcalcifications in Underlying Adolescent Hashimoto's Thyroiditis: A Case Report

Hashimoto's thyroiditis is the most common diffuse thyroid disease and is characterized by diffuse lymphocytic infiltration. However, the ultrasonographic findings of papillary thyroid carcinomas that arise from Hashimoto's thyroiditis in the pediatric and adolescent population are not well known.We report a rare ultrasonographic finding in a 22-year-old woman diagnosed with the diffuse sclerosing variant of papillary thyroid carcinoma that arose from underlying Hashimoto's thyroiditis: innumerable diffuse microcalcifications instead of a typical malignant-appearing nodule.

Papillary Thyroid Carcinoma Arising in Children and Adolescent Hashimoto's Thyroiditis: Ultrasonographic and Pathologic Findings

Objectives. We compared the ultrasonography and pathology features of papillary thyroid carcinoma (PTC) in pediatric and adolescents with Hashimoto's thyroiditis (HT) with those of non-HT patients. Materials and Methods. Eleven patients who were surgically confirmed to have pediatric or adolescent PTC from 2006 to 2014 were included in this study. We retrospectively analyzed the preoperative ultrasonography and pathology features of PTC arising in HT and non-HT patients. Results. On ultrasonography, thyroid gland was lobulated and enlarged, with many scattered microcalcifications in four of five HT patients. Four of six non-HT patients had suspicious masses with calcifications. The diffuse sclerosing variant of PTC (DSVPTC) was found in three of five HT patients, but none in non-HT patients. Macroscopic or microscopic extrathyroidal extension was evident in all of the HT patients and four of the non-HT patients. Neck lymph node metastases were in all HT patients and five of non-HT patients. Conclusions. Three of five PTCs in pediatric and adolescent HT patients were DSVPTC, whereas all PTCs of the non-HT patients were classic type. On ultrasonography, thyroid gland was diffusely enlarged with scattered microcalcifications in four of five HT patients. All five HT cases had aggressive disease, including extrathyroidal extension and cervical lymph node metastases.

Intrathyroidal Ectopic Thymus in Children: Retrospective Analysis of Grayscale and Doppler Sonographic Features

OBJECTIVES

The purpose of this study was to define grayscale and color Doppler sonographic features of an ectopic intrathyroidal thymus and to differentiate it from other thyroid nodule etiologies.

METHODS

We retrospectively reviewed imaging findings from 30 children who had a diagnosis of an ectopic intrathyroidal thymus from November 2005 to January 2013. Nodular thyroid lesions that were enclosed by the thyroid parenchyma and showed a typical echo pattern consistent with the thymus were accepted as the enclosed form of an intrathyroidal ectopic thymus. Eleven of these 30 children had an intrathyroidal ectopic thymus enclosed by the thyroid parenchyma, and they were enrolled in the study. The recorded sonograms were reviewed according to side, location, size, shape, echo pattern, internal content, and vascularization.

RESULTS

The enclosed forms of ectopic intrathyroidal thymuses were unilateral in all children and located in the mid portion (n = 10) or lower portion (n = 1). All lesions were well demarcated, and the most common shape was fusiform (n = 8). Nine lesions showed a typical hypoechoic echo pattern with internal linear and punctate echoes resembling a mediastinal thymus. On color Doppler imaging, 6 lesions showed hypovascularity compared to the thyroid parenchyma, and 5 lesions showed internal vascularity.

CONCLUSIONS

Unique sonographic features of the enclosed form of an ectopic intrathyroidal thymus, including a hypoechoic echo pattern with multiple linear and punctate echoes, a fusiform shape, a well-demarcated contour, and a mid- or low-lying location with hypovascularity or internal vascularity, can help radiologists differentiate it from other thyroid nodule etiologies.

Ultrasonography of various thyroid diseases in children and adolescents: a pictorial essay

Thyroid imaging is indicated to evaluate congenital hypothyroidism during newborn screening or in cases of a palpable thyroid mass in children and adolescents. This pictorial essay reviews the ultrasonography (US) of thyroid diseases in children and adolescents, including normal thyroid gland development, imaging features of congenital thyroid disorders (dysgenesis, [aplasia, ectopy, hypoplasia], dyshormonogenesis, transient hypothyroidism, thyroglossal duct cyst), diffuse thyroid disease (Grave's disease, Hashimoto's thyroiditis, and suppurative thyroiditis), and thyroid nodules. The primary imaging modalities for evaluating thyroid diseases are US and radionuclide scintigraphy. Additionally, US can be used to guide aspiration of detected nodules.

Intrathyroidal thymic tissue mimicking a malignant thyroid nodule in a 4-year-old child

Intrathyroidal thymic tissue is rare and may be confused with a malignant thyroid nodule because of hyperechoic dots mimicking calcifications. We report the case of a thyroid nodule with malignant ultrasonographic findings in a 4-year-old child, which was confirmed cytologically as ectopic thymic tissue. The sonographic findings of ectopic thymus were similar to those of the thymus; therefore, clinicians should be familiar with ultrasonography findings of normal thymic tissue.

Thyroid disease in children: part 2 : State-of-the-art imaging in pediatric hyperthyroidism

Hyperthyroidism occurs secondary to overproduction of thyroid hormone by the thyroid gland. This condition can have rather serious effects on children, and thus timely diagnosis and treatment are of utmost importance. Imaging is quite useful in the management of children with hyperthyroidism. In addition to determining the underlying pathology, radiologic exams are crucial for therapy. This article describes the underlying etiologies of pediatric hyperthyroidism and provides general information on treatment.

Thyroid disease in children: part 1: State-of-the-art imaging in pediatric hypothyroidism

Hypothyroidism, defined as inadequate production of thyroid hormone, can be secondary to various underlying abnormalities in the pediatric population. Most frequently, hypothyroidism is related to structural abnormalities of the gland (dysgenesis), particularly in the neonatal population. However, other etiologies including intrinsic biochemical (dyshormonogenesis) and autoimmune abnormalities, as well as other rare causes, must be considered. Imaging is required to differentiate among the various etiologies of hypothyroidism and can be helpful in guiding therapy. This review aims to present an organized approach to hypothyroidism in the pediatric population, and assist the imager in guiding patient care.

Intrathyroidal thymic tissue mimicking a thyroid nodule in a 4-year-old child

A 4 year-old girl was referred for CT of her neck for suspected submental lymphadenopathy and was found to have an incidental low-attenuation thyroid mass. Subsequent thyroid ultrasound showed a heterogeneous thyroid mass with punctate areas of increased echogenicity. Cytologic examination was consistent with ectopic intrathyroidal thymic nodule. We review the presentation of ectopic thymic tissue, especially in the thyroid gland.

Thyroid nodules in pediatrics: which ones can be left alone, which ones must be investigated, when and how

Thyroid nodules are less frequent in childhood than in adulthood, but are more often malignant. Recent estimates suggest that up to 25% of thyroid nodules in children are malignant, therefore, a more aggressive approach is recommended. In this review, we suggest an approach based on a first-step clinical, laboratory, and sonographic evaluation. A history of irradiation of the neck, cranium or upper thorax, previous thyroid diseases or thyroid neoplasms in the family should alert clinicians as being associated with a greater likelihood of malignant nodules. Signs or symptoms of hyperthyroidism and dysmorphic features should be carefully considered during the physical examination. Palpable firm lymph nodes, found in some 70% of cases, are the most significant clinical finding in children with malignant nodules. Although the routine determination of calcitonin levels is not uniformly practiced, it can help recognize sporadic or familial medullary thyroid neoplasms. Blood thyroid stimulating hormone, free thyroxine, and free triiodothyronine determinations (the latter in case of symptoms of hyperthyroidism) are aimed at identifying the few hyperthyroid patients, for whom the next step should be scintiscan. Hyperthyroid patients usually disclose an increased uptake, and a diagnosis of toxic adenoma is commonly made. Cases with normal thyroid function or hypothyroidism (which is usually subclinical) should be evaluated by fine-needle aspiration biopsy (FNAB). In eu/hypo-thyroid patients, scintiscan provides poor diagnostic information and should not be routinely employed. Thyroid ultrasonography is used to select cases for FNAB. Although ultrasound cannot reliably discriminate between benign and malignant lesions, it does provide an index of suspicion. Sonographic features that increase the likelihood of malignancy are microcalcifications, lymph node alterations, nodule growth under levothyroxine treatment, and increased intranodular vascularization demonstrated by color Doppler. There is growing evidence that elastography may provide further information on nodule characteristics. FNAB is indicated in all cases with a likelihood of malignancy. FNAB has a diagnostic accuracy of approximately 90% and is used in selection of patients which require surgery. Recently, histological markers and elastography have been introduced to increase the specificity of FNAB and ultrasound, respectively. The pitfall in FNAB cytology is the follicular cytology, in which it is not possible to distinguish between adenoma and carcinoma and therefore thyroidectomy is advised.

Incidental thyroid abnormalities identified on neck US for non-thyroid disorders

BACKGROUND

Incidental thyroid abnormalities detected on US examinations in children have not been well documented.

OBJECTIVE

To determine prevalence of incidental thyroid abnormalities depicted by US in children and to describe the spectrum of appearances.

MATERIALS AND METHODS

Retrospective analysis of clinical and US findings in children who had neck US from January 2006 to December 2007.

RESULTS

Of 1,228 neck US exams, thyroid was depicted in 287 children (mean age = 6.2 years). Incidental thyroid abnormalities were detected in 52 (18%) (mean age = 8.1 years). In 35 there were small (<4 mm), well-defined cysts, some with a hyperechoic punctate focus. In nine there were hypoechoic, solid nodules with smooth, straighter margins with echogenicity similar to thymus, suggesting intrathyroid ectopic thymus (mean age = 2.5 years). In three others there were tiny hyperechoic foci without nodules. Other abnormalities included hypoechoic target-like lesions (n = 2), isoechoic nodule (n = 1), multiple hypoechoic foci (n = 1) and non-visualized thyroid lobe resulting from adjacent abscess (n = 1). None of the children developed thyroid dysfunction or malignancy.

CONCLUSION

There is a spectrum of incidental thyroid abnormalities in children. These US findings should be interpreted cautiously, avoiding unnecessary referrals and investigations. Intrathyroid ectopic thymus is more common than previously thought, occurs much more frequently in younger boys and should be considered if the lesion has US characteristics of thymus.

Evolution of sonographic appearance of the thyroid gland in children with Hashimoto's thyroiditis

BACKGROUND

Although thyroid ultrasound is a valuable tool for the diagnosis and follow-up of patients with Hashimoto's thyroiditis (HT), classical sonographic findings are not always present.

AIM

To calculate the time needed for children with HT and normal ultrasound at diagnosis to develop characteristic sonographic findings.

PATIENTS AND METHODS

105 children (23 male and 82 female) with HT (mean age 9.4 +/- 2.9 years) were studied. Physical examination and measurements of TSH and fT4 levels were performed at diagnosis, at 3-month intervals for the first year, and twice yearly thereafter. Thyroid ultrasound was performed at diagnosis and twice yearly thereafter. The median follow-up duration was 18 months (range: 6-61 months).

RESULTS

The time needed for 30%, 50%, and 70% of children to demonstrate an abnormal thyroid sonographic pattern was 4, 7, and 14 months, respectively. Important factors accelerating sonographic changes were goiter (p = 0.023), hypothyroidism (p = 0.0255), and seropositivity for both thyroid peroxidase (anti-TPO) and thyroglobulin (anti-Tg) autoantibodies (p = 0.0005).

CONCLUSION

Sonographic findings of HT are present in 37% of children at diagnosis. Fifty percent of children with normal initial thyroid US will develop changes within 7 months; however, characteristic findings may not develop for over 4 years.

Sonography of the pediatric thyroid: a pictorial essay

The purpose of this article is to review the various pediatric thyroid diseases using sonographic images. These diseases included congenital hypothyroidism (dysgenesis [aplasia; ectopy; hypoplasia], dyshormonogenesis, transient hypothyroidism), thyroglossal duct cyst, Graves' disease, Hashimoto's thyroiditis, suppurative thyroiditis, nodular hyperplasia (goiter) and thyroid mass. Thyroid sonogram is the primary method used for thyroid disease and can be used for guiding of fine needle aspiration to obtain a more accurate diagnosis for suspected thyroid lesions.