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 posttreatment imaging studies in patients with a history of well-differentiated thyroid cancer, particularly in young adults who have received radioiodine therapy. Recognition of the possible coexistence of this incidental finding in patients with thyroid cancer may help to avoid unnecessary invasive procedures and treatments.