A six-year-old boy with a suspicious thyroid nodule: intrathyroidal thymic tissue

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.

Long-Term Follow-Up Ultrasonographic Findings of Intrathyroidal Thymus in Children

Objective

To analyze long-term follow-up sonographic findings of intrathyroidal thymus in children.

Materials and Methods

Among 1259 patients with congenital hypothyroidism under 15 years of age who underwent thyroid ultrasonography (US), 41 patients were diagnosed with an intrathyroidal thymus based on US criteria, i.e., hypoechoic solid lesion with punctate and linear echogenicity. In 26 patients aged one to 14 years old, the last follow-up US was performed after 6 to 132 months and compared with the initial US. The lesion was considered to decrease in size if there was a change of more than 2 mm in any dimension. The margin change was divided into well-defined and indistinct, blurred. When the echogenicity changed to a hyperechoic from a characteristic thymic echogenicity pattern, the pattern was considered a hyperechogenic. The changes in size were compared with the changes in shape, margin, and echogenicity pattern. The changes in size, shape, margin, and echogenicity were analyzed the association with the age of last follow-up. Statistical analysis was conducted using the chi-squared test and logistic regression.

Results

Fifteen (57.7%) cases were stable in size, and 11 (42.3%) decreased in size, including one that disappeared. Ten (38.5%) cases changed to indistinct margins from initially well-defined margins including one case of initially indistinct margin. Six (23.1%) changed to hyperechogenic, from initially characteristic thymic echogenicity patterns. When follow-up change was compared, decreases in size were significantly associated with lesion changes to indistinct margins (p = 0.004). The age at last follow-up was significantly associated with change to hyperechogenicity (odd ratio, 2.141; 95% confidence interval, 1.144–4.010, p = 0.017).

Conclusion

On follow-up US, an intrathyroidal thymus may be decreased in size, with indistinct margins, or show changes to a hyperechoic mass. Decreases in size may be associated with changing to indistinct margins, and changes to hyperechogenicity may be associated with increasing age.

Long-term ultrasound follow-up of intrathyroidal ectopic thymus in children

OBJECTIVE

To present the sonographic follow-up of intrathyroidal ectopic thymus (IET) in children and adolescent patients.

PATIENTS

Out of the 507 children referred to FNAB between 2006 and 2018, 30 (5.9%) pediatric patients (10 females), mean age 5.7 years (1.2-13.8, median 4.9 years) were diagnosed with IET.

METHODS

A retrospective analysis of medical files of patients diagnosed with IET between 2006 and 2018. Assessed data included ultrasound characterisation, elastographic strain ratio (SR) results and hormonal evaluation.

RESULTS

Analysis of thyroid US scans revealed that the mean age at the first thyroid ultrasound was 5.7 (1.2-13.8, median 4.9) years, and at the last US 10.7 (3.7-18, median 10.5) years. The mean time of the IET observation was 59.6 (2-148, median 53.5) months. On US, IET was hypoechoic with multiple linear and punctate echoes, hypovascular, fusiform on longitudinal plane and round or polygonal on an axial plane, more common in the right thyroid lobe (66.7%) and located in the posterior part of the lobes (54.5%), bilateral in two patients and multifocal in one patient. SR of IET was similar to the surrounding normal thyroid tissue. Complete regression of IET was observed in 12/30 patients after a mean time of 81.7 months (median 76.5), at the mean age of 13.7 (9.2-18, median 13.9) years. FNAB was performed in 10/30 and a hemithyroidectomy in 1/30 IET patients. In the FNAB (+) group, patients were younger (5.08 vs 6.08 years) and lesions were larger (0.12 ml vs 0.05 ml) than in the FNAB (-) group. All patients with IET were euthyroid with negative TPOAb and TgAb levels.

CONCLUSION

The reproducibility of unique ultrasound features of IETs allows for safe long-term follow-up of these benign lesions in the majority of pediatric patients: not only monitoring the regression of IET but also screening towards the rare occurrence of a tumor arising from the IET.

Adult Ectopic Cervical Thymic Tissue in relation to a Parathyroid Adenoma and a Papillary Thyroid Carcinoma: A Report of Two Cases

Ectopic cervical thymus is a rare congenital anomaly, which results because of the failure of complete descent of the thymus. They are incidental findings in the young and may disappear during the early years of life; however, they have rarely been described in adults. Some of them may undergo hyperplasia or neoplastic transformation and become visible or cause symptoms. We report two rare cases of incidentally detected cervical thymic tissue in adults. In one case, the thymic tissue was seen adjacent to a parathyroid adenoma of the left inferior parathyroid gland. In the other, it was seen adjacent to the left inferior parathyroid gland in a case of papillary thyroid carcinoma. In both these cases, the ectopic thymic tissue was diagnosed as a result of pathological examination, not clinically by macroscopic appearance during operation or radiological evaluation. The finding needs to be noted as these ectopic foci can occasionally give rise to hyperplasia and neoplasms of the thymus.

Intrathyroidal ectopic thymus in 8-year-old girl: a case report

We provide a case report of two thyroid nodules in an 8-year-old girl, which revealed malignant ultrasonographic findings and which were confirmed as ectopic thymic tissue by total thyroidectomy. The ultrasound presentations of intrathyroidal thymus glands were similar to those of the malignant thyroid nodules. In addition, in this case, there were two ectopic thymus lesions in the thyroid gland, which undoubtedly increased the difficulty of diagnosis. The occurrence of multiple ectopic thymic lesions in the thyroid gland was different from previous reports. Therefore, clinicians should take into consideration this rare entity, and should not mistake it as a thyroid neoplasm; moreover, they should not perform extensive thyroid resection.

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.

Prevalence and sonographic features of ectopic thyroidal thymus in children: A retrospective analysis

PURPOSE

To assess the prevalence of ectopic thyroidal thymus tissue detected by sonography (US) in children and to analyze the US features.

METHODS

We retrospectively reviewed images of 216 children who had undergone a thyroid or neck US examination from February 2015 to June 2015. Lesions within or adjacent to the thyroid gland that showed echopatterns consistent with thymic tissue were diagnosed as ectopic thyroidal thymus tissue. Lesions were reviewed according to their side, location, level, size, shape, echo pattern, internal content, and vascularization.

RESULTS

A total of 216 children (119 girls, 97 boys) with a mean ± SD age of 8.6 ± 5.2 years were enrolled the study.Thirty children (13girls, 17 boys) (13.9%) had 35 lesions compatible with ectopic thyroidal thymus tissue.Nine children had intrathyroidal (4.2%) and 21 children had extrathyroidal (9.7%) ectopic thymus tissue.The mean ± SD ages of the children with and without ectopic thyroidal thymus tissue were 6.0 ± 3.6 years and 9.1 ± 5.2 years, respectively (P = .002). Twenty-five of the lesions were extrathyroidal and 10 were intrathyroidal. All extrathyroidal and most (8/9) intrathyroidal ectopic thymuses had fusiform shape with well demarcated contours. Ectopic thymuses were located either in the midportion (n = 23) or lower portion of the neck (n = 12). Both extrathyroidal and intrathyroidal ectopic thymuses showed typical hypoechoic (n = 22/25, n = 9/10, respectively) or hyperechoic (n = 3/25, n = 1/10, respectively) echo patterns with internal linear and punctate echoes.

CONCLUSIONS

Ectopic thyroidal thymic tissue is common in children. Radiologists should be vigilant about the unique US features of ectopic thyroidal thymus, including a hypo- and hyper-echoic echo pattern with multiple linear and punctate echoes, a fusiform shape, well-demarcated contours, and middle or low-lying location to differentiate it from other neck or thyroid lesions.

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.

Ectopic Intrathyroidal Thymic Tissue Mimicking Thyroid Nodules in Children

Ectopic intrathyroidal thymic tissue is a benign lesion of nonthyroid origin occasionally found in the pediatric thyroid gland. Accurate diagnosis of such lesions is critical to avoid unnecessary biopsy or surgery. Twelve children referred to our center for the concern of thyroid nodules were found to have intrathyroidal thymic tissue. Most of the lesions had a classic sonographic appearance of a hypoechoic mass with sharp margins and multiple focal internal nonshadowing echogenicities identical to thymic tissue. Sonography and, in select cases, fine-needle aspiration can be used to diagnose benign thymic tissue within the thyroid and avoid unnecessary surgery.

Ectopic Intrathyroidal Thymus in Childhood: A Sonographic Finding Leading to Misdiagnosis

BACKGROUND

During gestation, the primordial thymus migrates from the pharynx to the anterior mediastinum, thus thymic tissue can remain at any point along this path. Intrathyroidal thymic remnants are rare, and their sonographic patterns have only recently been described. This retrospective study presents the sonographic appearance of ectopic intrathyroidal thymus and emphasizes the role of sonography in order to avoid misdiagnosis.

METHODS

The population consisted of 42 children, 3.5-14 years old, who had a thyroid sonogram performed due to a positive family history or symptoms indicative of thyroid disease, and ectopic intrathyroidal thymus was recognized.

RESULTS

In all patients, the same pattern was revealed: a fusiform intrathyroidal lesion, with no mass effect, homogeneously hypoechoic, with diffuse bright internal echoes. The similarity to the characteristic sonographic pattern of the normal mediastinal thymus was crucial for the diagnosis of ectopic intrathyroidal thymic tissue. In 8 cases, a normal elongated thymus was found connected to the thyroid with an accessory lobe embedded in the lower thyroid pole. The above sonographic appearances mimicked a thyroid nodule.

CONCLUSIONS

Awareness of the sonographic patterns of the ectopic intrathyroidal thymus is mandatory to avoid misdiagnosis. In most cases, further investigation is unnecessary, but sonographic follow-up should be recommended.

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.

Intrathyroidal ectopic thymic tissue mimicking thyroid cancer in children

OBJECTIVE

To increase awareness of the important differential diagnosis between thyroid cancer and intrathyroidal ectopic thymic tissue when performing neck ultrasound (US) in pediatric patients.

METHODS

We report 2 cases of intrathyrodal thymic tissue that were initially referred as possible papillary thyroid cancer (PTC). US and cytologic features of these lesions are described, and the distinguishing US characteristics of intrathyroidal thymic tissue versus PTC are discussed.

RESULTS

Two pediatric patients who underwent thyroid US were diagnosed with thyroid nodules suggestive of PTC. The suspected lesions in both patients exhibited an echo texture identical to the normal thymus gland. Fine-needle aspirate (FNA) biopsy of the nodule in the first case revealed numerous lymphocytes with positive immunocytochemical staining for CD3, confirming a T cell phenotype. The second patient underwent follow-up US imaging 8 months later that showed stability of the intrathyroidal nodule.

CONCLUSION

Intrathyroidal ectopic thymic tissue can be mistaken for PTC as both conditions have similar US features. Increased awareness of this unique mimicry may help to avoid unnecessary invasive investigations and surgery in these young patients.

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.

Sonographic appearance of intrathyroid ectopic thymus in children

PURPOSE

The aim of this study is to report the common location of intrathyroid ectopic thymus and describe the corresponding sonographic appearances in children.

METHODS

We retrospectively reviewed clinical data and neck or thyroid ultrasonography (US) findings in children from January 2003 to May 2010. Intrathyroid lesions showing hypoechogenicity with multiple linear echogenic branching structures or punctate echogenic foci were considered intrathyroid ectopic thymus. US features of the lesions (location, side, size, and shape) and the indication for US were recorded.

RESULTS

A total of 5,414 neck or thyroid US examinations were conducted in 3,195 children. We found 15 lesions that were suspected of being intrathyroid ectopic thymus in 12 patients (0.4%), four boys and eight girls, with a mean age of 6.4 years. The lesions were unilateral in nine patients and bilateral in three patients. All the lesions were located at the mid to lower portion of the thyroid. The long-axis diameter of the lesions ranged from 0.7 to 2.2 cm (mean diameter: 1.5 cm). All lesions had a fusiform shape with well-defined margins.

CONCLUSIONS

The possibility of intrathyroid ectopic thymus should be considered when a mid- to low-lying intrathyroid lesion with a fusiform shape with multiple linear or punctate internal echoes is detected on US in children.

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.

Selective pathologies of the head and neck in children: a developmental perspective

The range of pathology seen in the head and neck region is truly amazing and to a large extent probably mirrors the complex signaling pathways and careful orchestration of events that occurs between the primordial germ layers during the development of this region. As is true in general for the entire discipline of pediatric pathology, the head and neck pathology within this age group is as diverse and different as its adult counterpart. Cases that come across the pediatric head and neck surgical pathology bench are more heavily weighted toward developmental and congenital lesions such as branchial cleft anomalies, thyroglossal duct cysts, ectopias, heterotopias, choristomas, and primitive tumors. Many congenital "benign" lesions can cause significant morbidity and even mortality if they compress the airway or other vital structures. Exciting investigations into the molecular embryology of craniofacial development have begun to shed light on the pathogenesis of craniofacial developmental lesions and syndromes. Much more investigation is needed, however, to intertwine aberrations in the molecular ontogeny and development of the head and neck regions to the represented pathology. This review will integrate traditional morphologic embryology with some of the recent advances in the molecular pathways of head and neck development followed by a discussion of a variety of developmental lesions finishing with tumors presumed to be derived from pluripotent/progenitor cells and tumors that show anomalous or aborted development.

Cytology and flow cytometry to identify ectopic thymic tissue masquerading as a thyroid nodule in two children

BACKGROUND

Clinically unapparent thyroid nodules in children pose a significant problem in differential diagnosis and management. Ectopic thymic tissue in the thyroid gland is rare, but may masquerade as a thyroid nodule. This paper demonstrates the utility of flow cytometry as an adjunct to cytology by fine needle aspiration in diagnosing ectopic thymic tissue in the thyroid gland.

SUMMARY

By demonstration of T lymphocytes maturing along two cell lineages and the absence of markers for malignant lesions, fine-needle aspiration, cytology, and flow cytometry were used to identify ectopic thymic tissue masquerading as a thyroid nodule in two children.

CONCLUSION

Use of this technique prevented surgical intervention that otherwise would have been necessary to obtain an accurate diagnosis of these thyroid nodules.

Intrathyroidal thymic tissue surrounding an intrathyroidal parathyroid gland, the cause of a solitary thyroid nodule in a 6-year-old boy

Ectopic intrathyroidal thymic tissue is a rare occurrence; parathyroid glands sometimes occur in an intrathyroidal location, but this is uncommon. We report a 6-year-old boy who was noted to have a solitary thyroid nodule on ultrasound. A hemithyroidectomy was performed, and histological investigation revealed that the nodule consisted of ectopic intrathyroidal thymus tissue surrounding a well-defined parathyroidal gland. This condition is an exceedingly rare cause of a thyroid nodule, but intrathyroidal thymic tissue should probably be included in the differential diagnosis of solitary thyroid nodules.