Mediastinal Tumors



Mediastinal Tumors


Marcus E. Eby





  • The mediastinum is the central compartment of the thoracic cavity, which is surrounded by loose connective tissue and enclosed laterally by the left and right pleurae.


  • The mediastinum is the most common location of chest masses in children where a wide variety of both benign and malignant tumors may occur.1


  • Mediastinal tumors are classified based on 1 of 3 mediastinal compartments (anterior, middle, or posterior) in which they originate (Figure 52.1).


ANTERIOR MEDIASTINUM


Normal Contents



  • Thymus gland, internal mammary artery and vein, lymph nodes, and adipose tissue


Boundaries



  • Anterior: sternum


  • Posterior: the anterior pericardium


  • Lateral: parietal pleurae


  • Superior: imaginary line extending from sternal angle to T4 vertebrae


  • Inferior: surface of diaphragm


Most Common Anterior Mediastinal Neoplasms



  • Mnemonic: 4Ts = Teratoma (and other germ cell tumors), Terrible lymphoma, Thymoma, and Thyroid neoplasms (from ectopic thyroid tissue)


MIDDLE MEDIASTINUM


Normal Contents



  • Pericardium and its contents, ascending aorta, superior and inferior vena cava, brachiocephalic artery and vein, central portion of pulmonary arteries and veins, phrenic and upper vagus nerves, trachea, the main bronchi, and lymph nodes







Figure 52.1 Lateral chest radiograph showing mediastinal divisions. The anterior mediastinum (Ant Med) lies posterior to the sternum and anterior to a line drawn along the anterior tracheal wall in the upper mediastinum and the posterior border of the heart in the lower mediastinum. The posterior mediastinum (Post Med) lies posterior to a line 1 cm behind the anterior margin of the vertebral column and anterior to the chest wall. The middle mediastinum (Mid Med) lies between these. (Reprinted with permission from Webb WR, Higgins CB. Thoracic Imaging. 2nd ed. Philadelphia, PA: Wolters Kluwer/Lippincott Williams & Wilkins Health; 2010.)


Boundaries



  • Anterior and posterior: the pericardium


  • Lateral: parietal pleurae


  • Superior: imaginary line extending from sternal angle to T4 vertebrae


  • Inferior: surface of diaphragm


Most Common Middle Mediastinal Neoplasms Bronchogenic Cyst



  • Lymphoma, cardiac tumor, cystic hygroma, pericardial cyst


POSTERIOR MEDIASTINUM


Normal Contents



  • Descending aorta, esophagus, thoracic duct, azygos and hemiazygos veins, and lymph nodes



Boundaries



  • Anterior: the posterior pericardium


  • Posterior: T5-T12 vertebrae


  • Lateral: parietal pleurae


  • Superior: imaginary line extending from sternal angle to T4 vertebrae


  • Inferior: surface of diaphragm


MOST COMMON NEOPLASMS



  • Neurogenic tumors, meningomyelocele, neuroenteric abnormalities



    • Note: the most common pediatric mediastinal mass = neurogenic tumor (˜20% of all mediastinal tumors), usually found in the posterior mediastinum.2


    • As mediastinal masses can be either benign or malignant, definitive tumor diagnosis via biopsy (obtained via CT guided, bronchoscopy, or surgical) is desired before definitive intervention to determine the nature of the tumor and whether chemotherapy might reduce the size of the tumor for easier resection if indicated.2



OVERVIEW



  • Neurofibromas are nerve-sheath tumors that can arise from peripheral nerves, sympathetic ganglia, or mediastinal chemoreceptors of the paraganglion system3,4


  • Most common benign tumor of the mediastinum in children


  • Most frequently located in the posterior mediastinum



    • Note: neurofibromas can present in isolation or as one of multiple tumors seen in neurofibromatosis type 1


PRESENTATION



  • Often presents with tracheal compression as tumor grows in size, resulting in upper respiratory symptoms or with the development of scoliosis; usually first suspected on plain radiographs and confirmed with MRI (Figure 52.2)


SURGICAL INTERVENTION

May 5, 2019 | Posted by in PEDIATRICS | Comments Off on Mediastinal Tumors
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