Mediastinum
- Region between the pleural sacs
Has 3 compartments
- anterior
- middle
- posterior
- Thymus
- Anterior mediastinal lymph nodes
- Internal mammary A & V
- Pericardial fat
Contents of the Middle Mediastinum
- Heart & Pericardium, ascending aorta & arch of aorta, vena cavae, brachiocephalic A &V ,
- phrenic nerve
- trachea, main stem bronchi & contiguous lymph nodes
- Pulmonary A & V
Contents of the Posterior Mediastinum
- Descending thoracic aorta
- Esophagus
- Thoracic duct
- Azygos & hemiazygos vein
- Posterior group of mediastinal nodes
- Sympathetic trunk & intercostal nerves
- Anterior - sternum
- Posterior - Vertebral Column
- Superior - Thoracic inlet
- Inferior - Diaphragm
** Mediastinum is connected to neck & retroperitoneum allowing spread of air & infection
Masses in the Anterior Mediastinum (4 T's) (30% of mediastinal masses)
- Thymoma
- Teratoma
- Thyromegaly
- Terrible Lymphoma
- Lipoma, Fibroma - rare
Masses in the Middle Mediastinum (30% of mediastinal masses)
- Aneurysms - aorta, innominate artery, enlarged pulmonary artery
- Lymphadenopathy secondary to carcinoma / metastasis / granulomatosis
- Cysts - enteric, bronchogenic, pleuropericardial
- Dilated azygos, hemiazygos veins
- Hernia of Foramen of Morgagni
Masses in the Posterior Mediastinum (40% of mediastinal masses)
- Neurogenic tumors
- Meningo-myelocele, meningocele
- Esophageal - tumor, cyst, diverticula
- Hiatus hernia
- Hernia of Foramen of Bochdalek
- Thoracic spine disease,
- Extramedullary hematopoiesis
Pediatric Presentation
- 33% of all masses present in patients less than 15 years old
- If small, usually asymptomatic and found incidentally (cautious work up)
 If large, usually present with respiratory distress (frantic work up)
Differential Diagnosis
Lymphoma
- Most common pediatric mediastinal malignancy
- may be found in any compartment of the mediastinum
Neurogenic
- Ganglioma, ganglioneuroblastoma, neuroblastoma, paraganglioma
- Most common benign lesions
- 2nd most common malignant lesions
- Most often in posterior mediastinum
Teratoma
- common found in the anterior mediastinum
- with malignancy potential
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