Abstract
Mediastinal teratomas are rare germ cell tumors that account for only a small proportion of pediatric mediastinal masses. Usually, they remain asymptomatic and are incidentally detected. However, in infants, large teratomas may rapidly become life-threatening due to their compressive symptoms. We report a rare case of a 7-month-old male who presented in the emergency with a large left-sided anterior mediastinal mass with severe respiratory distress and underlying collapsed lung. This case emphasizes the importance of considering mediastinal teratomas as the differential diagnosis of pediatric respiratory distress and also highlights the need for timely surgical intervention.