Mediastinal Mass



Mediastinal Mass


Leslie S. Kersun



INTRODUCTION

The mediastinum is a potential space within the thoracic cavity, between the two pleura. It is divided into anterior, middle, and posterior regions. The etiology of a mediastinal mass is often suggested by its regional location because it likely formed from the normal structures in that area.



  • Anterior Mediastinum

    Anatomy: The anterior mediastinum is bounded by the first rib superiorly, the posterior surface of the sternum anteriorly, the anterior border of the upper dorsal vertebra posteriorly, and by an imaginary curved line that follows the cardiac border and extends backward until it reaches the border of the dorsal vertebra.

    Structures: This area contains structures anterior to the pericardium including the thymus, lymph nodes, and, rarely, extension of the thymus gland. The superior vena cava (SVC) is an easily compressible, thin-walled vessel with a low intraluminal pressure that is surrounded by the lymph nodes and thymus.


  • Posterior Mediastinum

    Anatomy: The posterior mediastinum is bounded posteriorly by the anterior surface of the curve of the ribs, anteriorly by the posterior border of the pericardium, and inferiorly by the diaphragm.

    Structures: The primary structures in this area are the sympathetic ganglia, descending aorta, thoracic duct, and esophagus.


  • Middle Mediastinum

    Anatomy: The middle mediastinum is the area between the anterior and the posterior regions with the diaphragm as its base.

    Structures: This region contains the trachea, bronchi, heart, great vessels, and the majority of the mediastinal lymph nodes.



image HINT: SVC syndrome is generally associated with anterior mediastinal masses.



DIFFERENTIAL DIAGNOSIS LIST


Anterior Mediastinum



  • Germ cell tumor


  • Hemangioma


  • Histiocytosis


  • Leukemia


  • Lipoma


  • Lymphangioma (cystic hygroma)


  • Lymphoma—non-Hodgkin lymphoma (NHL), Hodgkin lymphoma (HL)


  • Substernal thyroid


  • Teratoma


  • Thymic hyperplasia or cyst


  • Thymoma


Middle Mediastinum



  • Bronchogenic cyst


  • Castleman disease


  • Fibromatosis histoplasmosis


  • Pericardial cyst


  • Sarcoidosis


  • Tuberculosis (TB)


  • Vascular anomalies


Posterior Mediastinum



  • Esophageal duplication cyst


  • Thoracic meningocele


  • Tumors of neurogenic origin—neuroblastoma, ganglioneuroblastoma, ganglioneuroma, neurofibroma, and schwannoma

Note: Ewing sarcoma and rhabdomyosarcoma can form masses in any of the mediastinal regions.


DIFFERENTIAL DIAGNOSIS DISCUSSION


Anterior Mediastinum



image HINT: Most (70%) anterior mediastinal masses in children are malignant.


Superior Vena Cava Syndrome/Superior Mediastinal Syndrome

SVC and superior mediastinal (SM) syndromes are life-threatening complications of anterior mediastinal masses. SVC syndrome implies venous obstruction from compression or thrombosis. When coupled with tracheal compression, the syndrome is called SM syndrome. Tracheal compression without signs of venous obstruction is more common and equally worrisome. The mediastinal mass compresses the SVC, the trachea, or both, impeding blood return and air flow and producing the signs and symptoms summarized in Table 52-1.

These are rare syndromes; only 10% to 15% of pediatric patients with malignant anterior mediastinal tumors have SVC syndrome or SM syndrome. However, it is critical to recognize these patients because their condition can deteriorate dramatically and quickly. Immediate consultation with an oncologist is always appropriate.


Leukemia

Patients with lymphoblastic leukemia (most often T-cell) can present with a mediastinal mass. This is the most likely diagnosis when there are concurrent abnormalities in the complete blood count (anemia, thrombocytopenia, neutropenia,
or leukocytosis) or circulating peripheral blasts. In these patients, the diagnosis is most easily made by bone marrow aspirate. In patients with hematologic malignancies, lumbar puncture may be combined with other diagnostic procedures in order to simultaneously assess malignant involvement of the spinal fluid.








TABLE 52-1 Signs and Symptoms of Superior Vena Cava Syndrome or Superior Mediastinal Syndrome






























History

Physical Examination


Cough, especially when supine

Retractions


Dyspnea or orthopnea

Wheezing or stridor


Headache

Papilledema


Dizziness or syncope, especially when symptoms are exacerbated with Valsalva maneuver

Prominence of neck or chest veins


Facial swelling

Suffusion or edema of face, neck and conjunctiva


Visual changes

Anxiety or confusion


Sense of fullness in ears

Quiet heart sounds, hypotension or pulsus paradoxus if cardiac tamponade

Cyanosis or plethora



Lymphoma



image HINT: Lymphoma is the most common cause of SVC and SM syndromes in children.


Non-Hodgkin Lymphoma

Mediastinal masses in patients with NHL are often caused by lymphoblastic lymphoma; however, it can also be secondary to diffuse large B-cell lymphoma (see Chapter 50, “Lymphadenopathy”). Approximately 60% of patients with lymphoblastic lymphoma present with a mediastinal mass, and they often have associated pleural or pericardial effusions.

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Sep 14, 2016 | Posted by in PEDIATRICS | Comments Off on Mediastinal Mass

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