Ectopic Cervical Thymus

Abstract

Ectopic cervical thymic tissue is an uncommon cause of neck masses in children, with fewer than 100 cases reported in children who presented with primary neck masses. To illustrate the unique characteristics of these tumors, we report the case of a 13-month-old boy with ectopic thymic tissue presenting with asymptomatic, bilateral, and solid cervical masses. This case report highlights several unique findings: (1) the rare nature of solid thymic tumors compared with cystic lesions, (2) the utility of magnetic resonance imaging scanning with and without fat suppression for diagnosis, and (3) the risks of surgical removal of thymic tissue in children. Despite its infrequent occurrence and often asymptomatic presentation, ectopic cervical thymus masses should be included as a rare cause of cervical masses in the pediatric population. Awareness of this diagnosis will allow for appropriate preoperative diagnostic studies, which may preclude the need for biopsy.

Ectopic cervical thymus: Recognising the characteristic ‘embroidery yarn’ appearance on ultrasound

“…A cystic lesion is the more common sonographic appearance. 7 However, it is the solid lesion that is often concerning for more serious pathologies such as malignant masses. Ultrasound appearance of the solid ectopic thymus is similar to that of the normal mediastinal thymus.…”

A “no-touch” neck “mass” in a child

“…Cervical thymus although a rare entity should be kept in the differential diagnosis of asymptomatic neck masses in children. [10] e unique imaging findings on ultrasound and MRI paralleling that of the normal thymus tissue should aid to confidently establish the diagnosis. e radiologist must be aware of the condition and the typical normal appearance of thymus which can obviate the need for biopsy or surgical intervention.…”

Ectopic cervical thymus in children: Clinical and radiographic features

“…The thymic primordia forms from the ventral aspect of the third and fourth pharyngeal pouch. In the sixth week, the thymopharyngeal duct forms and gradually detaches from the pharynx, forming a tube‐like structure that migrates caudally toward the mediastinum . Arrest of migration in the superior neck may leave patients with Type D lesions, which tend to be larger in size and are typically diagnosed at a young age.…”

“…Around the 10th week of gestation, solid cords connecting the primordia to the pharynx are obliterated . Remnants of these solid cords in the central neck may produce Type C lesions if they are associated with the thyroid gland, or Type B lesions if not.…”