Thymic hyperplasia after chemotherapy for ovarian malignancy: two cases complicated by hyperthyroidism

Thymic hyperplasia is a benign condition in which the thymus enlarges in response to various stimuli. It occasionally occurs after chemotherapy for hematologic malignancies or in association with hyperthyroidism, but no previous reports describe cases in which multiple causes coexist. We present two cases of thymic hyperplasia occurring after chemotherapy for ovarian malignancy, both accompanied by concurrent hyperthyroidism. Case 1 was a 29-year-old woman with ovarian dysgerminoma, Stage IC1, and Case 2 was a 46-year-old woman with ovarian high-grade serous carcinoma, Stage IIIB; both patients received surgery and chemotherapy. Twelve and twenty-four months after completion of chemotherapy, computed tomography revealed an anterior mediastinal mass. Additional imaging showed no malignant features. They were diagnosed with thymic hyperplasia. Screening tests later identified hyperthyroidism in both women, and medical therapy was initiated. These cases highlight that thyroid function testing should be considered when thymic hyperplasia is detected in young female patients with malignancy.