What is Mediastinal Mass?
Mass formation occurs due to the excessive, abnormal growth of tissues due to anomalous cell division. Mediastinal mass may be cancerous or benign in nature, which is formed in the chest wall present between the two lungs. Due to the site is termed as mediastinum, so the name of the mass is medically termed as mediastinal mass.
Mediastinum Location AND Organs
Other than lungs, various vital organs such as heart, aorta, trachea, esophagus and thymus are associated organs in the mediastinum. Therefore, the mediastinum is surrounded by several protective skeletal structures, which include a sternum (breastbone) sited in front, spine is located at back.
The mediastinum is divided into three locations and the mass can form in any segments of the mediastinum. Thus, mediastinal mass is further classified into three types depending upon the location:
- The anterior mediastinal mass (front): Thymomas and lymphomas (both Hodgkin and non-Hodgkin)
- The posterior mediastinal mass (back): Neurogenic tumors and esophageal abnormalities
- The superior mediastinal mass present above the thoracic plane (upper side): Neoplastic and non-neoplastic pathology.
- The inferior mediastinal mass present below the thoracic plane (lower side): The inferior segment is further divided into three divisions and mass can shape any of these three divisions, which comprise the central segment which contains the pericardium and the major blood vessels and respiratory organs; the frontal segments, which lies at the interior part of the sternum; and the posterior segment , which lies in between sternum and spine. (1,2,3,4)
Causes
The primary three types of mediastinal mass are considered in medical science and different research finds the possible cause behind the formation of mediastinal mass. These are discussed below:
Anterior mediastinum mass
The possible causes involve in anterior mediastinum mass are
Germ cell
These cells are involved in gamete production and present in both the gender. Due to abnormal cell division (neoplasm) cause the development of the mediastinum mass, though this is benign in nature.
Lymphoma
The involvement of the lymph nodes causes malignant mass formation and usually classified as Hodgkin’s disease and non Hodgkin’s lymphoma.
Thymoma and thymic cyst
One of the common type of Anterior mediastinum mass is the formation of a thymic cyst. This type of cyst is mostly benign laceration, which is located within a fibrous capsule. This type of mediastinum mass is more destructive, as it can cause continual invasion throughout the fibrous capsule.
Thyroid mass mediastinal
This is mainly benign and formed due to nutritional deficiency or other factors which provides abnormality in the thyroid gland.
Middle mediastinum
The possible causes involve in middle mediastinum mass are:
Bronchial cyst
The mass is originated from the bronchi or bronchus and usually benign in nature.
Lymphadenopathy mediastinal
Abnormal growth formed in the lymph nodes.
Pericardial cyst
Evagination of the lining of the heart or pericardium can cause benign cyst formation.
Thyroid mass mediastinal
This is mainly benign and formed due to nutritional deficiency or other factors which provides abnormality in the thyroid gland. Goiter formation is also can progress to middle mediastinum mass.
Tracheal tumors
Respiratory involvement, such as abnormal cell growth in tracheal cells can cause malignant or benign mass formation, such as tracheobronchopathia osteochondroplastica, which is a benign tumor.
Vascular abnormalities, including bulge formation in the aorta (aortic aneurysm) and tearing of the inner lining of the aorta (aortic dissection).
Posterior mediastinum
Extramedullary haematopoiesis
Bone marrow expansion rarely causes mediastinum mass formation, which is associated with severe anemia.
Lymphadenopathy mediastinal
An extension of the lymph nodes.
Neuroenteric cyst mediastinal
When both neurological and gastro-intestinal abnormality insisted mass formation cause posterior mediastinum mass.
Neurogenic neoplasm mediastinal
Neuronal involvement is one of the commonest reason of posterior mediastinal tumors. Different types neuronal involvement includes nerve sheath neoplasms, paraganglionic cell neoplasms, and ganglion cell neoplasms. Almost 70% of neurogenic neoplasms are benign.
Esophageal anomaly includes esophageal neoplasm, achalasia esophageal neoplasm and hiatal hernia. Para-spinal abnormality including infection, malignancy and trauma of the thoracic vertebrae. (1,3,5,6)
Differential Diagnosis
The different differential diagnosis for mediastinal mass the following tests are conducted:
Chest X-Ray
Chest X ray is a preliminary test, which often used as incidental diagnostic tool, means during other chest related symptomatic reason detection performed X-ray image provides the reflection of mediastinal mass.
Computer Tomography (CT) Scan with IV contrast
This is an advanced imaging technology, which can help to detect fluid-filled or fatty cystic mass. In addition, it is a first round test for detecting any mass is benign in nature.
Mediastinoscopy with biopsy
This is test is done for confirmatory test for malignant mediastinal mass. This test almost provide an accurate result, but it is mild invasive process. In this test, a small sample of cell sample is collected from the mediastinum.
This test is conducted in a clinic or hospital setting by providing general anesthesia, as this test requires small notch under the sternum. The collected tissue from the mass send to the tissue identification laboratory for diagnose the metastasis of the cell.
Needle aspiration or needle biopsy
This test is also provided definite result. Needle aspiration is preferred for malignant lesions. But this technique cannot be useful, if the doctor suspects the involvement of the thymoma, lymphoma, or a neural mass. In these cases, cutting-needle biopsy provides reliable result.
Thyroid Stimulating hormone (TSH) measurement
If the doctor suspected that ectopic thyroid tissue involvement, then he may order for specific test considered for thyroid-stimulating hormone measurement.
Other than these, some doctors also prefer to perform MRI and tissue examination. (1,3,5,6)
References
1. Mediastinal Tumor (2011); Cleveland Clinic; Retrieve from: https://my.clevelandclinic.org/services/heart/disorders/hic_mediastinal_tumors
2. Tim Luijkx and A.Prof Frank Gaillard et al.; Differential for an anterosuperior mediastinal mas; Retrieve from: http://radiopaedia.org/articles/differential-for-an-anterosuperior-mediastinal-mass
3. Camilla R. Whitten, Sameer Khan, Graham J. Munneke, and Sisa Grubnic, (2007); A Diagnostic Approach to Mediastinal Abnormalities; Retrieve from: http://pubs.rsna.org/doi/full/10.1148/rg.273065136
4. Henry Knipe and Dr Jeremy Jones et al.; Mediastinal mass; Retrieve from: http://radiopaedia.org/articles/mediastinal-mass
5. Richard W. Light (2014); Mediastinal Masses; Retrieve from: https://www.msdmanuals.com/professional/pulmonary-disorders/mediastinal-and-pleural-disorders/mediastinal-masses
6. Darla Burke (2016); Mediastinal Tumors (Neoplasms); Retrieve from: http://www.healthline.com/health/mediastinal-tumor#Overview1
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