Ectopic cervical thymic tissue: can imaging obviate biopsy and surgical removal?

Abstract

Thymic tissue rests can be found all along the route of thymic descent from the neck into the anterior mediastinum and are frequently misinterpreted as pathological masses, which leads to biopsy or surgical removal. We present a case of ectopic thymic tissue in the neck and review the imaging characteristics of our patient and those found in the literature to determine if biopsy for this normal variation can be avoided. US findings of ectopic tissue reveal the exact tissue characteristics of normal thymus. The ectopic thymus may have an angulated configuration and mold over adjacent structures rather than displacing or invading them. If further verification is needed, T1-weighted MR images show homogeneous isointense or slightly hyperintense tissue compared with muscle and T2-weighted images show hyperintensity. The mass has the same structure as the normal thymus. We believe, on the basis of these findings, that one can confidently avoid the need for biopsy to prove that the discovered mass is ectopic thymus tissue.

Aberrant cervical thymus and the role of ultrasonography: A case report

“…The entire or partial thymus may also fail to descend 1,3 . In patients with an undescended thymus, only half or less of the thymus is present in the chest 4 . The latter presents as a larger ectopic neck mass.…”

“…Cervical thymus is an uncommon cause of neck mass and usually detected incidentally 4 . Eighty % to 90% of these lesions remain asymptomatic.…”

“…They also reported that ultrasound characteristics of thymic tissue are unique enough to make a diagnosis of aberrant cervical thymus and biopsy may not be required for the diagnosis 1 . Zielke et al 4 also concluded that the mass in question is ectopic thymic tissue can be confirmed by US, depending on the unique imaging features. Thus, biopsy or surgical removal may not be required.…”

“…Also, to the best of our knowledge there is not enough data to point out that the malignant transformation rate of ectopic thymic tissue is any greater than normal thymic tissue. Thus, patients with aberrant cervical thymus could be followed without resection 4 .…”

“…It can occur anywhere along the pathway of thymic descent (thymopharyngeal duct) from the angle of the mandible to the superior mediastinum [1][2][3] . With the advent of high-frequency ultrasound probes, it is now possible to demonstrate the similarity of echotexture between the thymus and neck mass 4 . Unique features of the thymus anatomy (internal echo characteristics) allows the diagnosis.…”