Doctors use many tests to diagnose cancer and determine if it has spread. Some tests may also determine which treatments may be the most effective. A biopsy is the only way to make a definitive diagnosis of lymphoma. Imaging tests may be used to find out whether the lymphoma has spread. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
• Type of lymphoma suspected
• Severity of symptoms
• Previous test results

To determine if a person has NHL, the doctor will first take a complete medical history and do a physical examination, paying special attention to the lymph nodes, liver, and spleen. The doctor will also look for signs of infection that may cause the lymph nodes to swell and may prescribe an antibiotic. If the swelling in the lymph nodes still does not go down after antibiotic treatment, the swelling may be caused by something other than an infection. If the doctor suspects lymphoma, he or she will recommend a biopsy, as well as laboratory and imaging tests.

In addition to a physical examination, the following tests may be used to diagnose NHL:

Biopsy [2]. A biopsy is the removal of a small amount of tissue for examination under a microscope. To diagnose lymphoma, the most common type is a biopsy of lymph nodes in the neck, under an arm, or in the groin. A biopsy may also be taken from the chest or abdomen during a computed tomography (CT) scan (see below) or from the stomach or intestine during an endoscopy (a test that allows the doctor to see inside the body with a thin, lighted, flexible tube). A biopsy of the skin may also be needed depending on the suspected subtype of lymphoma. A biopsy is the only way to make a definite diagnosis of lymphoma and find out the subtype. Having enough tissue is important to make a diagnosis. The tissue sample removed during the biopsy should be analyzed by a pathologist experienced in the diagnosis of lymphoma; second opinions [3] may also be helpful.

Bone marrow biopsy and aspiration [4]. These two procedures are similar and often done at the same time. Bone marrow has both a solid and a liquid part. A bone marrow biopsy is the removal of a small amount of solid tissue using a needle. An aspiration removes a sample of fluid with a needle. The sample(s) are then analyzed by a pathologist. The most common site for a bone marrow biopsy and aspiration is the iliac crest of the pelvic bone, located in the lower back of the hip. The skin and bone in that area are numbed with medication beforehand, and other types of anesthesia (medication to block the awareness of pain) may be used.

Lymphoma often spreads to the bone marrow, so looking at a sample of the bone marrow can be important for doctors to diagnose lymphoma and to determine the stage. The sample removed during the aspiration is also used to find any chromosome changes.

Molecular testing. Your doctor may recommend running laboratory tests on the lymphoma cells to identify specific genes, proteins, chromosome changes, and other factors unique to the disease. Results of these tests will help decide on your treatment options.

Computed tomography (CT or CAT) scan [5]. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. A CT scan can also be used to measure the size of a tumor. Sometimes, a contrast medium (a special dye) is injected into a patient’s vein or given orally to provide better detail and find the exact position of a tumor. A radiologist (a doctor who specializes in performing imaging tests to diagnose disease) interprets CT scans. CT scans of the chest, abdomen, and pelvis can help find cancer that has spread to the lungs, lymph nodes, and liver.

Magnetic resonance imaging (MRI) scan [6]. An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium may be injected into a patient’s vein to create a clearer picture. A radiologist interprets the scan. 

Positron emission tomography (PET) scan [7]. A PET scan is another imaging test that can help find cancer in the body. A small amount of a radioactive substance (called radioactive glucose) is injected into a patient’s body. This substance is absorbed mainly by organs and tissues that use the most energy. Because cancer tends to use energy actively, it absorbs more of the substance. A scanner then detects this substance to produce images of the inside of the body. A nuclear medicine physician interprets the scan.

How well PET scans work for learning more about NHL is not yet clear, although aggressive lymphomas often show up on PET scans. Many doctors will recommend a PET scan as part of the initial diagnosis, especially for aggressive lymphomas. PET scans for lymphoma are being researched, and it’s not yet clear if they are helpful to stage [8] or monitor indolent lymphomas during treatment.

Learn more about what to expect when having common tests, procedures, and scans [9].

After these diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor describe the cancer; this is called staging [8]. Learn more about the first steps to take after a diagnosis of cancer [10].