Mediastinal tumors

What are mediastinal tumors?

Mediastinal tumors are space-occupying masses in the so-called mediastinum. The mediastinum is an anatomical space in the chest cavity, located between both lungs and bounded anteriorly by the sternum and posteriorly by the spine. It contains many organs and structures, the heart being the most prominent. Other structures include the thymus gland, lymph nodes and lymphatic vessels, as well as blood vessels and nerves.

The heart is located in the center of the mediastinum, which can be divided further into an anterior, middle, and posterior segment. This distinction can be very helpful for localizing and identifying a tumor in this region.

Although the term ‘tumor’ is most commonly associated with cancer, the term describes a growth in tissue volume, which can be either malignant or benign. Therefore, a tumor does not automatically indicate a malignant disease.

Overall, mediastinal tumors are rare. In children, mediastinal tumors are most commonly located in the posterior segment and originate from nervous tissue. In contrast, adults aged between 30 and 50 are most frequently affected by tumors arising in the anterior segment of the mediastinum. 

What are the different types of mediastinal tumors?

A mediastinal tumor is often used as an umbrella term to describe various types of space-occupying lesions. They can be further classified based on their malignancy status and location.

Benign mediastinal tumors

Cysts are common benign mediastinal tumors. They are fluid-filled cavities that are surrounded by a capsule. They can generally form in all tissues and organs, for example common locations include the ovaries, the thyroid, the kidneys, or the skin. Mediastinal cysts are often congenital and are diagnosed incidentally. Therefore, they do not necessarily require treatment.

Similarly, an increase in thymic tissue in the anterior segment can be benign. The thymus gland belongs to the lymphatic organs and is responsible for the maturation of important immune cells, particularly the so-called T-cells. The thymus is relatively large in size in children and adolescents but shrinks with increasing age. A benign increase in thymic tissues can be observed in various diseases such as myasthenia gravis, an autoimmune condition in which signal transmission between nerve cells and muscle cells is disrupted.

Other benign space-occupying lesions of the mediastinum include benign germ cell tumors, nervous tissue tumors (neurinomas), and enlarged lymph nodes. Furthermore, an aortic aneurysm may cause a swelling in the mediastinum. However, this is not a tumor but rather a dilation of the diameter of the aorta. 

Malignant mediastinal tumors

The most common malignant mediastinal tumors are thymomas, which are located in the anterior segment and are also referred to as thymic tumors. Despite thymomas accounting for approximately 20% of all mediastinal tumors, they are still a rare condition. Both benign and malignant thymic tumors are associated with myasthenia gravis. This means that approximately 45% of patients with thymoma also have myasthenia gravis.

Moreover, another group of mediastinal tumors are lymphomas. These are malignant cell proliferations arising from lymphatic tissue. Depending on the respective cell type, they can be further classified into B- and T-cell lymphomas. Another distinction is based on the presence of specific cells resulting in the classification into Hodgkin- and non-Hodgkin lymphomas. 

Malignant germ cell tumors represent another group of malignant mediastinal tumors. They arise from the displacement of embryonic tissue into the chest cavity. Embryonic cells can differentiate into various tissue types. Therefore, there are many different germ cell tumor types, including teratomas, which can be malignant or benign. 

What are the causes and risk factors?

Tumors form when there is an abnormal increase in body tissues, either through cell enlargement or multiplication. Malignant tumors are characterized by their invasive growth. Tumor cells multiply uncontrollably, while displacing and infiltrating surrounding healthy tissue. Once the tumor grows into blood or lymphatic vessels, it can form secondary deposits, so-called metastases, in distant organs.

Various mechanisms can lead to changes in tissues, many of which are still being researched. For example, the exact mechanisms for the development of thymic carcinomas have not been identified yet. Similarly, the explanation as to why they are associated with various conditions such as myasthenia gravis or rheumatic diseases is also largely unknown.

However, several risk factors have been identified for the development of lymphomas. Various infectious diseases are known to promote their development, such as HIV infections and infections with herpesviruses, for example Epstein-Barr virus (EBV). Moreover, cell-toxic substances can trigger a lymphoma, including benzene-containing solvents, immunosuppressive medications or previous radiotherapy.

What symptoms are common?

In most cases, mediastinal tumors are diagnosed incidentally, as they often cause no symptoms. They can become noticeable on an X-ray, for example during the examination of the chest or ribs. 

When symptoms arise, they are usually caused by the displacing growth of the tissue. They can trigger chest pain or a feeling of pressure. If the tumor starts pressing on nearby organs, that may cause symptoms such as coughing, difficulty swallowing, hoarseness or shortness of breath. 

Lymphomas can cause more general symptoms rather than space-occupying symptoms. A typical constellation of symptoms is the so-called B-symptoms, which consist of unintentional weight loss, fever and night sweats. Displacement of blood cells in the bone marrow can also lead to anemia, increased susceptibility to infection and a tendency to bleed. 

How is a mediastinal tumor diagnosed?

If a space-occupying lesion in the mediastinum is suspected, this warrants prompt diagnostic workup. The method of choice is a computed tomography (CT) of the chest with an intravenous contrast agent. This can provide initial clues about the nature of the tumor as well as compression of neighboring structures.

In some cases, further imaging may be required, such as MRI or PET-CT. Blood tests may also provide further clues about the nature of the tumor. The primary aim of the diagnostic workup is to assess the accessibility and the feasibility of completely removing the tumor or obtaining a biopsy to establish a definite diagnosis.

How does a specialist treat a mediastinal tumor?

The treatment of mediastinal tumors generally consists of surgical removal of the tumor. If this is not possible, the aim is to obtain a tissue sample, a so-called biopsy. This particularly applies to lymphomas. Further treatment depends on the specific type of tumor.

Benign tumors usually do not require further treatment. In some cases, even a biopsy may not be necessary if imaging provides reliable information about the nature of the tumor. However, a decision regarding the necessity of surgical removal must always be made on a case-by-case basis.

In the case of malignant tumors such as thymic carcinomas or germ cell tumors, complete removal is particularly important. Depending on the exact location and size of the tumor, different surgical methods are available. Open surgery involves opening the sternum (sternotomy) while minimally invasive techniques require only small skin incisions.

The treatment of lymphomas follows a completely different approach. After obtaining a biopsy and confirming the definite diagnosis of a lymphoma, the aim is no longer surgical removal but rather systemic treatment. The treatment of choice is system therapy such as chemotherapy.

What are the prognosis and chances of recovery?

The chances of recovery from mediastinal tumors primarily depend on the resectability of the tumor. If the tumor can be surgically removed in its entirety, the chances of recovery are generally very good. This applies particularly to benign tumors.

The prognosis of lymphomas primarily depends on the tumor’s response to the chemotherapeutic agents. The chances of recovery are generally better when the less disease is less extensive and an appropriate therapy is initiated sooner. The average 10-year survival rate of patients with non-Hodgkin lymphoma is approximately 60% in Germany.

Which physicians and clinics are specialists in mediastinal tumors?

As mediastinal tumors comprise a group of very different tumor entities, physicians from various specialties are often involved in the care. The diagnostic methods are conducted by specialist radiologists or nuclear medicine specialists. Specialist surgeons are trained in the removal of mediastinal tumors and in obtaining biopsies. In the case of malignant tumors, specialist oncologists become involved.

We aim to support patients in finding competent and experienced physicians who specialize in the diagnosis and treatment of mediastinal tumors. We have thoroughly reviewed and selected all of the below-listed specialists. They are all experts in treating mediastinal tumors. Benefit from their experience and professional expertise and arrange an initial consultation.