Mediastinal Lymph Nodes

Mediastinal lymph nodes are lymph nodes located in the mediastinum. Mediastinum is a term that refers to the idea of a sort of "box" or zone within the chest, but it also implies all of what is inside the box. The mediastinum can be thought of as a cube: bordered on two sides by the lungs; on the front, by the breastbone; on the back, by the backbone; at the top, by the outlet to the neck; and at the bottom, by the chest floor, or diaphragm muscle that helps the lungs expand and contract with breathing. Inside the chest, if you imagine your lungs as two huge balloons hogging up all the space, there is a pocket or space in between them. The mediastinum refers to that pocket or box that is jam-packed with organs including the heart, blood vessels, nerves, lymph nodes and other important structures.

If your mediastinal lymph nodes are enlarged, you should know that there are many different possible reasons for this finding. This is something that is generally true of all enlarged lymph nodes.

Mediastinal lymph nodes, in particular, can become enlarged on their own, or along with other illnesses, including certain diseases that affect the lungs. While enlarged mediastinal lymph nodes may in some cases be a sign of cancer, lymph node enlargement in this area commonly results from other, noncancerous diseases. In fact, people with chronic obstructive pulmonary disease (COPD), a very common respiratory disorder, may have enlarged mediastinal nodes owing to that condition, especially if they have a strong bronchitis component of their disease.

When your doctor needs to make a determination about the cause of enlarged nodes in the mediastinum, you may have a procedure called mediastinoscopy with biopsy. A small surgical cut is made just above the sternum or breastbone. An instrument called a mediastinoscope is inserted through this cut and carefully passed into the mid-part of the chest where tissue samples can be taken of the lymph nodes. This procedure is done in the hospital under general anesthesia. In many cases, the results of the biopsy are ready in five to seven days.

Lymph nodes are small structures located all over the body. Lymph nodes in the mediastinum, or mediastinal lymph nodes, are important medically for many different reasons—one of them being that they can potentially indicate the presence of cancer.

Not all swollen lymph nodes in the chest are lymphoma, or even cancer, however. Infection and nonmalignant diseases like sarcoidosis may be to blame. In countries where tuberculosis is common, this infection can be a leading cause of mediastinal lymph node enlargement. Something called anthracosis can also cause these lymph nodes to enlarge. Anthracosis, or miner's lung, is the accumulation of carbon in the lungs due to repeated exposure to air pollution or inhalation of smoke or coal dust particles.

When lymph nodes in the chest are enlarged due to cancer, lymphoma and lung cancer are two common possibilities. Cancer from other sites can also metastasize or spread to these lymph nodes.

Lymphoma, a cancer of the lymphocyte white blood cells, has two basic categories—Hodgkin lymphoma and non-Hodgkin lymphoma.

Hodgkin lymphoma, or HL, often starts with the mediastinal lymph nodes. The chest is involved in 85 percent of all cases of HL, whereas in non-Hodgkin lymphoma, or NHL, the figure is closer to 45 percent.

While HL typically progresses in an orderly fashion from one group of lymph nodes to the next, the same may not be true for many common NHLs, although some can have a more orderly Hodgkin's-like behavior.

While chest imaging can identify suspicious looking lymph nodes, the initial diagnosis of lymphoma, regardless of type, is made by biopsy.