To review the embryological development of the thymus (the origin in the third pharyngeal pouch,
the thymopharyngeal duct and its descend path to the superior mediastinum);
To review the appearance and report our experience with cervical thymic anomalies at US,
MR and PET-CT imaging;
To show examples of ectopic cervical thymic tissue,
anomalies related to thymoparyngeal remnants and the superior cervical extension of the thymus;
To discuss the differential diagnosis and the management of these cervical lesions.
The pharyngeal glandular organs have complex developmental origins.
and ultimobranchial bodies,
develop and migrate concurrently from their sites of origin to their final positions along the ventral midline of the pharyngeal and upper thoracic region.
The thymus originated from a ventral sacculation of the 3rd (and probably 4th) pharyngeal pouch on each side,
during the 6th week of gestation.
Endodermal cells proliferation within the sacculation gives rise to a thymic primordium (ectodermal and mesenchymal elements are further incorporated).
Findings and procedure details
Appearance of Normal Thymus
The thymus has a hypoechogenic and slightly heterogeneous echotexture.
In infants it shows multiple thin echogenic lines and branchings.
In older child and adults we identify multiple hyperechogenic foci which give to the thymus a distinct appearance that resembles a "starry sky".
In adults the thymic parenchyma may be more echogenic due fatty infiltration.
The thymus size and shape can vary greatly even among individuals in the same age group.
Thymus has a soft...
Cervical thymic anomalies are uncommon and are rarely considered in the differential of a neck mass.
They are often identify during childhood and usually presents as asymptomatic nodule or neck swelling on routine examination.
The thymus has a unique appearance at ultrasound allowing for an accurate diagnosis in most of the cases.
Familiarity with the spectrum of imaging appearance of the cervical thymic anomalies may help minimize invasive procedures,
especially in children.
If ectopic thymus causes symptoms,
due to compression or pressure in the neighboring...
NS et al. Superior Cervical Extension of the Thymus: A Normal Finding That Should Not Be Mistaken for a Mass.
JY et al. Multimodality Imaging Evaluation of the Pediatric Neck: Techniques and Spectrum of Findings.
EG et al. Ectopic Cervical Thymic Tissue: Diagnosis by Fine Needle Aspiration.
Arch Pathol Lab Med,
I et al. Ectopic Thymic Tissue as a Rare and Confusing Entity.
Eur J Pediatr Surg,