Ectopic thymus (left neck lump)

Case contributed by Dr Jeremy Jones


Left sided neck mass referred from an external center. MRI performed externally.

Patient Data

Age: 3 months old
Gender: Male

Performed externally prior to referral

Left neck mass is traversed by vessel.  Iso-to-muscle T1, Hyperintense-to-muscle T2, no fat-suppression, no enhancement.  There is a tongue of tissue that extends towards the carotid sheath, passes between the internal and external carotid just distal to the bifurfaction and then extends caudally.


The left neck mass is demonstrated to have ultrasound characteristics of thymus and demonstrated in continuity with the thymus in the upper mediastinum via the tongue of tissue that extends between the internal and external carotid arteries.

Case Discussion

This case demonstrates a very rare cause of neck mass at the angle of the mandible in a child. Here, the cause is ectopic thymic tissue which would be expected to involute as the normal thymus does in childhood.

Over an extended period of follow up, the neck lump reduced in size. Biopsy was not performed.

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Case information

rID: 26783
Published: 8th Jan 2014
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

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