Enlarged lymph nodes, which are clusters of lymph tissue that contain immune cells, in the lungs can be caused by both common and uncommon infections, immune system disorders, or cancer, according to Mayo Clinic.
Lymph nodes are major sites where immune cells and foreign substances interact, as reported by eMedicineHealth. These substances can be infectious microorganisms, such as viruses, cancerous cells or the body's own tissue. Lymphadenopathy, or enlarged lymph nodes, in and around the lungs can indicate an infection in the chest, such as the common cold or the flu, or a more serious infection like tuberculosis, as reported by Mayo Clinic.
Enlarged lymph nodes can also indicate more serious complications, according to Mayo Clinic. Certain immune system disorders, such as lupus and rheumatoid arthritis, are caused by the body's immune cells and antibodies attacking its own tissues. These autoimmune disorders can cause lymphadenopathy in any part of the body that is being affected. Cancer that causes lymphadenopathy can also originate in the lungs or metastasize to the lungs from other sources. Many health care professionals test for cancer primarily if lymphadenopathy is found in the lungs, since this condition is only noticed once the cancerous cells have begun to spread.