What does a sonogram on a swollen lymph node show?

It depends: It depends on why the lymph node is swollen. Enlargement can be from the body's reaction to infection or inflammation, sometimes an abscess can form inside a lymph node. Cancer can also spread through lymph nodes. Typically, unless the lymph node is biopsied the exact cause of the enlargement is not 100% certain. Remember, it is normal to have enlarged lymph nodes from time to time.