Getting a Diagnosis Before you have any tests, your doctor will want to know: How have you been feeling? Your doctor will check you for signs of lymphoma and will feel for swollen lymph nodes. Most of the time, an infection -- unrelated to cancer -- causes swollen lymph nodes. You might get a lymph node biopsy to check for cancer cells. It checks the number of certain cells in your blood. It uses radiation in low doses to make images of the inside of your chest. It uses powerful magnets and radio waves to make pictures of organs and structures inside your body. It uses a radioactive substance to look for cancer cells in your body.