Intrathyroidal ectopic thymus tissue: a diagnostic challenge

Significance of ectopic intrathyroidal thymic tissue detected on ultrasound in different paediatric age groups: a proposed classification to guide investigation and management

Ectopic aberrant thymic tissue is most commonly found in the thyroid gland and is increasingly found incidentally due to the widespread use of ultrasound. Correct identification of this benign pathology on ultrasound can avoid the morbidity associated with fine needle aspiration (FNA) and anxiety associated with a possible cancer diagnosis. A case series of 21 children found to have likely intrathyroidal thymic tissue on ultrasound scan of the neck between 2013 and 2024 at the University College London Hospital. Twenty-one children aged between six months and ten years old, 52% male and 48% female. The scans were performed following referral for a neck lump or cervical lymphadenopathy (N = 15), sore throat/cough (N = 4), pre-thyroidectomy scan for a Multiple Endocrine Neoplasia 2 patient (N = 1), and post cystic hygroma excision routine scan (N = 1). These well-defined hypoechoic foci ranged in size from 3 to 14 mm and direct comparison to normal thymic tissue was possible in 19/21 (90%). Three patients (14%) went on to have FNA to rule out papillary thyroid cancer (PTC); other cases had interval scans at median six months to confirm stable appearances.

CONCLUSION

All patients in our study with intrathyroidal ectopic thymic tissue were younger than 10 years. We suggest a tailored management approach based on the age at presentation, presence of clear thymic tissue for comparison and past/family history. Given that it is unlikely for such tissue to be present in older children, an FNA would be recommended to exclude underlying thyroid cancer in children over 14 years.

WHAT IS KNOWN

• Intrathyroidal thymic tissue is a common variant that will be increasingly incidentally picked up on ultrasound scans in chlidren.

WHAT IS NEW

• We suggest separation of children with ectopic intrathyroidal thymic tissue into three groups based on age and the ability to compare directly with normal thymic tissue.

[Intrathyroidal thymus can cause confusion in the diagnosis of a thyroid mass. A case report]

Intrathyroidal thymus tissue (ITTT) is a rare, benign condition; its diagnosis can prove challenging due to unfamiliarity with this entity. However, it has ultrasonographical and cytological characteristics which can suggest its presence and thus should be considered in the differential diagnosis of thyroid nodules. Presently, immunohistochemistry can be used with fine needle aspiration (FNA) cytology, thus decreasing the need for unnecessary surgery. We discuss the usefulness of immunohistochemistry in thyroid cytology, with reference to a case of a 10-year-old patient, who underwent partial thyroidectomy for a suspicious thyroid nodule which was eventually diagnosed as ITTT by the histopathology of the surgical specimen.

Echographic findings in ectopic intrathyroidal thymic tissue in children. A systematic review

Intrathyroidal ectopic thymic tissue (IETT) is an indulgent, unusual entity and is part of the differential diagnosis of thyroid nodules in the pediatric population. Because of the low prevalence of IETT, the diagnosis may be difficult. Awareness of this diagnosis is definitive to avoid surgical interventions. The aim of this study was to review the literature on the echographic characteristics of IETT. We conducted a search of Ovid, PubMed and the virtual health library. A total of 619 patients with a mean age of 6.2 years old were included. IETT was located in the lower portion of both of the thyroidal lobes in 556 children, the echographic shape was reported for 173 patients, with the fusiform shape as the most representative, the appearance of the IETTs was reported for 121 patients, the most common was the hypoechogenic pattern with multiple internal echogenic foci. The average lesion diameter was 5.53 mm, and Doppler findings reported a hipovascular pattern in 56% of the lesions. In conclusion, IETT is an infrequent entity; nonetheless, it must be considered in the differential diagnosis of neck nodules in children and should be study and follow with echography to avoid unnecessary surgery.

Dual energy CT in gland tumors: a comprehensive narrative review and differential diagnosis

Dual energy CT (DECT)with image acquisition at two different photon X-ray levels allows the characterization of a specific tissue or material/elements, the extrapolation of virtual unenhanced and monoenergetic images, and the quantification of iodine uptake; such special capabilities make the DECT the perfect technique to support oncological imaging for tumor detection and characterization and treatment monitoring, while concurrently reducing the dose of radiation and iodine and improving the metal artifact reduction. Even though its potential in the field of oncology has not been fully explored yet, DECT is already widely used today thanks to the availability of different CT technologies, such as dual-source, single-source rapid-switching, single-source sequential, single-source twin-beam and dual-layer technologies. Moreover DECT technology represents the future of the imaging innovation and it is subject to ongoing development that increase according its clinical potentiality, in particular in the field of oncology. This review points out recent state-of-the-art in DECT applications in gland tumors, with special focus on its potential uses in the field of oncological imaging of endocrine and exocrine glands.

Narrative review of multiparametric ultrasound in parotid gland evaluation

Disorders affecting parotid gland represent a heterogeneous group comprising congenital, inflammatory and neoplastic diseases which show a focal or diffuse pattern of appearance. The differentiation of neoplastic from non-neoplastic conditions of parotid glands is pivotal for the diagnostic imaging. Frequently there is evidence of overlapping between the clinical and the imaging appearance of the various pathologies. The parotid gland is also often object of study with the combination of different techniques [ultrasound-computed tomography-magnetic resonance imaging (US-CT-MRI), ex.]. Compared to other dominant methods of medical imaging, US has several advantages providing images in real-time at lower cost, and without harmful use of ionizing radiation and of contrast enhancement. B-mode US, and the microvascular pattern color Doppler are usually used as first step evaluation of parotid lesions. Elastography and contrast-enhanced US (CEUS) has opened further possible perspectives to improve the differentiation between benign and malignant parotid lesions. The characterization of the parotid tumors plays a crucial role for their treatment planning and for the prediction of possible surgical complications. We present, here an updated review of the most recurrent pathologies of parotid gland focusing on the diagnostic power of multiparametric US including CEUS and ultrasound elastography (USE); limitations, advantages and the main key-points will be presented.

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.

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.