How can we identify that the lymph is of cancer or not?

Biopsy: The most reliable way to determine if a lymph node contains cancer (be it from the spread of a cancer like breast cancer or a cancer of the lymph node itself such as lymphoma) is to obtain a piece of tissue. This can be obtained by an excisional biopsy (removal of entire lymph node) or by fine needle aspirate (fna). The tissue can then be examined by a pathologist to look for malignancy.