The most common cause of enlarged lymph nodes is infection. As lymph nodes are a part of the immune system that fights infections in the body, the presence of infection often causes lymph nodes to increase in size. All kinds of infections can cause node enlargement. As infections are far more common than cancers, enlarged nodes in the neck or groin are more often a sign of infection than a cancer. Learn more about the lymph system.
Some other immune diseases like sarcoidosis or lupus can also cause lymph node enlargement all over the body.
Some medicines and allergies can occasionally cause enlarged nodes.
Cancers other than lymphoma are also a common cause of lymph node enlargement. Throat cancer, oral cancer, and cancers of the lung or breast often spread to nodes in the neck. Breast or lung cancer can spread to nodes in the armpits. Uterine cancer, ovarian cancer, rectal cancer, and anal cancer can spread to the lymph nodes in the groin. Leukemia can also cause enlarged nodes in different parts of the body.
Children with some diseases that affect the body metabolism (called storage diseases) can have enlarged nodes.
Thus lymphoma is only one of the many possible causes of enlarged lymph nodes. A doctor will test you for many of these diseases before calling your enlarged lymph node a lymphoma.
The best test to determine whether a lymph node has lymphoma is a lymph node biopsy. If the lymph node tests positive for lymphoma, special tests may be carried out on the biopsy material to determine exactly which type of lymphoma it is, using the molecular markers for lymphoma.