Anterior mediastinal mature teratoma in a child presenting as a chest wall mass: A case report

Introduction Mature mediastinal teratomas are uncommon benign germ cell tumors that typically arise in the anterior mediastinum. Presentation as unilateral breast-region swelling is rare and can create diagnostic uncertainty. Case Presentation We report a 13-year-old boy who presented with progressive swelling of the left breast region following minor blunt chest trauma. Chest radiography showed a large opacity in the left hemithorax. Computed tomography (CT) of the chest revealed a large, complex anterior mediastinal mass measuring 12.8 × 10.3 × 12.1 cm (anteroposterior × transverse × craniocaudal), extending into the left anterior chest wall. The lesion was predominantly cystic, with enhancing solid components and areas of macroscopic fat, and without calcifications. Magnetic resonance imaging (MRI) excluded bony invasion. Tumor markers were within normal limits. The patient underwent complete surgical excision via a left thoracotomy, with chest tube placement. Histopathology confirmed a mature cystic teratoma, with no immature or malignant components. The patient recovered well postoperatively, and the chest tube was removed on postoperative day 3 followed by discharge home on postoperative day 5. At 1-year follow-up, the patient remained clinically asymptomatic, with follow-up MRI showing no evidence of local recurrence. Conclusion Mediastinal mature teratoma should be considered in the differential diagnosis of unilateral breast masses in children and adolescents.