FIGURE 98.1 Chest radiograph demonstrating a large, homogeneous anterior mediastinal mass Patient presented with persistent cough and progressive orthopnea Management Diagnostic workup in the ED should always include a chest radiograph, including a lateral view, to help establish the location of the mass Chest CT scan should only be performed in a patient who can comfortably lie supine CT contrast should not be given without verifying adequate renal function since TLS can occur Laboratory evaluations should include CBC to assess for evidence of marrow replacement and to identify circulating blasts Metabolic screening for possible TLS should be performed Patients with symptoms from an AMM must be admitted to a center with pediatric oncology expertise and may require critical care If an effusion is drained in the ED for relief of symptoms, a fluid sample should be sent to pathology for cytology if malignancy is suspected In general, patients who are not experiencing respiratory or hemodynamic compromise by an effusion should not have fluid drained for diagnostic purposes while in the ED