Incidental radiologic finding of an anterior superior mediastinal mass masquerading as metastatic thyroid cancer in patients with treated thyroid cancer.

Objective: To demonstrate that an anterior superior mediastinal mass on radiologic imaging may represent an incidental finding and not metastases in patients with a history of treated well-differentiated thyroid cancer.Methods: We report the clinical presentation and outcomes of 4 patients with a history of thyroid cancer who were incidentally found to have anterior superior mediastinal masses on imaging. We also review the relevant literature.Results: Four young adults with a history of stage I papillary thyroid cancer treated with total thyroidectomy and radioiodine were incidentally found to have thymic enlargement on imaging studies within a 3-year posttreatment window. In each case, this enlargement was believed to be secondary to thymic hyperplasia and not metastatic disease, and each patient has exhibited a benign clinical course. Review of the literature revealed few reports of an association between thymic hyperplasia and thyroid cancer.Conclusions: Thymic hyperplasia may be discovered on posttre...