Thymic hyperplasia in newly diagnosed testicular germ cell tumors

Thymic hyperplasia has been reported as a rebound phenomenon in children and young people, most commonly following chemotherapy for cancer. Although thymic hyperplasia has been documented in testis cancer patients after chemotherapy, to our knowledge it has not previously been reported in newly diagnosed cases before systemic therapy. A retrospective review of 362 testicular germ cell tumor patients treated at a single tertiary care center between January 1, 1980 and August 1, 1993 was performed, with special review of 221 who underwent computerized tomography staging of the chest. Thymic hyperplasia was detected in 4 of the 221 patients (1.8%) including 3 of 100 (3.0%) with seminoma and 1 of 121 (0.8%) with nonseminoma. All 4 patients had low stage (I or IIa) disease with a delay in diagnosis (5 to 24 weeks) and thymic hyperplasia was discovered at staging evaluation 18 to 37 days after orchiectomy but before other cancer therapy was administered. Of the 4 patients 2 underwent thymectomy, revealing histological thymic rebound hyperplasia. All 4 patients had no evidence of recurrence at 1 to 54 months after treatment. In addition to the well known post-chemotherapy phenomenon, thymic hyperplasia may also occur in nonsystemically treated, newly diagnosed testicular cancer patients. An anterior mediastinal mass in an otherwise low stage newly diagnosed testicular cancer patient may represent thymic hyperplasia and not necessarily metastatic disease.