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

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. (orig.)