recurrent laryngeal nerve is compressed as a result of the mass, hoarseness and inspiratory stridor may result Spinal cord compression and vertebral erosion can be seen with a posterior mediastinal tumor A careful history may reveal more subtle symptoms, and families should be queried specifically about fever, chills, weight loss, and night sweats Physical examination should be thorough It is important to focus on a careful respiratory and cardiac examination, evaluation of the head and neck for palpable masses or venous distention, palpation of the abdomen for organomegaly or masses, and examination of the various nodal basins for adenopathy Solid Mediastinal Masses Children with tumors of the anterior or superior mediastinum should be admitted to an inpatient ward for urgent evaluation because these tumors may pose an immediate threat to life CT scan or MRI of the chest is generally needed to supplement plain radiographs, in order to further define the location and extent of the mass, and to potentially provide details that may help establish the diagnosis Much of the management depends upon whether the lesion is cystic or solid Solid masses raise concern for oncologic pathology, particularly if located in the anterior mediastinum, and imaging may be very helpful in aiding diagnosis In the appropriate clinical setting, tumor markers should be obtained, including serum alpha fetoprotein (AFP) and beta-human chorionic gonadotropin (bHCG) levels, and urine catecholamine and metanephrine levels Lymphomas and teratomas are the most common mediastinal tumors in children, with other solid masses occurring more rarely Thymomas comprise less than 1% of mediastinal tumors in children, with multimodal therapy the mainstay Benign thymic hyperplasia typically does not cause respiratory compromise, but rapid enlargement often warrants intervention, such as steroid therapy or resection When biopsy of a large mediastinal mass is necessary, the logistics of the procedure require careful, thoughtful evaluation, ideally involving the pediatrician or emergency clinician, surgeon, oncologist, and anesthesiologist Airway and cardiac compression by large mediastinal masses can be significant Large mediastinal masses should be evaluated by CT scan of the chest to assess the presence and extent of tracheal compression MRI may be a better diagnostic modality for posterior mediastinal masses because many of them are neurogenic in origin and may have extension into the spinal canal An echocardiogram should also be obtained prior to surgery, to assess the extent of mediastinal shift and the degree of atrial or ventricular compression by the mass Delivery of general anesthesia may lead to occlusion of the thoracic trachea by the tumor This situation can be challenging to manage; passage of a rigid bronchoscope