Diagnosis

Clinical Presentation

Many mediastinal masses are asymptomatic (50%). In general, malignant lesions and masses in children are much more likely to cause symptoms. The most common symptoms are chest pain and weight loss. Lymphomas may manifest with fever and weight loss. In children, mediastinal masses are more likely to cause tracheobronchial compression and stridor or symptoms of recurrent bronchitis or pneumonia.

 

Symptoms and signs also depend on location. Large anterior mediastinal masses may cause dyspnea when patients are lying supine. Lesions in the middle mediastinum may compress blood vessels or airways, causing the superior vena cava syndrome or airway obstruction. Lesions in the posterior mediastinum may encroach on the esophagus, causing dysphagia or odynophagia.

o Chest X-ray

o CT scan

o MRI (depending on location)

o Pulmonary function tests for anterior mediastinal mass

o Appropriate tumor markers as indicated by clinical suspicion (AFP; β-HCG; urine for catecholamines and metanephrines)

Mediastinal masses are most often incidentally discovered on chest x-ray or other imaging tests during an examination for chest symptoms. Two-view chest radiographs often confirm the presence of mediastinal masses.

Ultrasound study can differentiate the cystic nature of the mass, but contrast-enhanced CT provides far more information about the mass and its relationship to the surrounding mediastinal structures.

MRI is helpful to define spinal involvement or vascular lesions. However, the sedation required for adequate MRI study in pediatric patients may compromise the airway in patients with large anterior mediastinal masses.

An esophagogram or echocardiogram also provides additional information to further define mediastinal masses.

Ultrasound or CT-guided percutaneous needle biopsy of solid mediastinal mass can be performed to establish tissue diagnosis. Complications such as pneumothorax, bleeding, perforation, or tumor seeding occur infrequently.

Tissue diagnosis may also be obtained from sites alternative to the tumor itself, such as lymph node or bone marrow. Incisional or excisional biopsies of the tumor are performed using thoracoscopy, mediastinoscopy or mini-thoracotomy. However, the goal of the preoperative work-up is to help define the optimal surgical approach for resection, and open direct tissue biopsy of masses is rarely indicated in pediatric patients.

Tumor markers such as serum β-human chorionic gonadotropin (β-HCG) or α-fetoprotein (AFP) may help in the diagnosis and follow-up of malignant mediastinal tumors. Since more than 90% of patients with neuroblastoma produce high levels of catecholamines, quantification of the corresponding by-products (vanillylmandelic acid, homovanillic acid) in urine over a 24-hour period can confirm the diagnosis.