Multilocular Thymic Cysts with Follicular Hyperplasia: Report of a Case

We herein describe a rare case of multilocular thymic cysts (MTCs) with follicular hyperplasia. The patient was a 50-year-old man, who was symptom-free. A mediastinal mass was found on chest computed tomography (CT) followed after pancreatitis. Chest CT revealed a 30 × 10 mm anterior mediastinal mass with multiple cystic lesions. Magnetic resonance imaging showed an anterior mediastinal cystic mass with low-signal intensity on T1-weighted image and on high-signal intensity T2-weighted image. Thus we made a preoperative diagnosis of MTCs with thymoma within the cyst wall. The lesion was resected by thymectomy. Intraoperatively, multiple cysts and swelling of mediastinal lymph nodes were noted throughout the entire thymus. Histopathological findings revealed lymphoid follicular hyperplasia of thymic tissues but no neoplastic lesions. Based on these findings, a diagnosis of MTCs associated with thymic hyperplasia was made. This is a rare case that preoperatively was difficult to diagnose.