Adult-Onset Hyperplasia of An Ectopic Cervical Thymus Associated with Uncontrolled Hyperthyroidism: A Case Report

Ectopic cervical thymus (ECT) is an essentially benign condition that is identified during the development of the thymus, and is rare among the adult population. Thymic hyperplasia is another thymus-associated condition, which is known to occur secondary to hyperthyroidism. A 39-year-old woman with hyperthyroidism presented with an enlarging submandibular mass, which was diagnosed as a benign hyperplasia of the ECT. Computed tomography and magnetic resonance imaging largely contributed to its diagnosis, and an unnecessary surgical resection was avoided. To the best of our knowledge, this is the first report that describes clinically significant hyperthyroidism-induced ECT hyperplasia during adulthood.