Cancer screens are tests that
help identify the presence of cancer before symptoms appear. Unfortunately,
there are presently no screening tests for lymphoma. As noted in the section on
diagnosis, the only definitive test for lymphoma involves biopsy (removal of a sample of suspected tumor tissue) and
examination of the cells for abnormalities. In some instances, doctors may
order tests on other body fluids, including:
- spinal tap:
spinal fluid sample, obtained by lumbar puncture
- bone marrow aspiration: liquid marrow sample
- peritoneal fluid analysis: fluid that accumulates in the abdomen
- pleural fluid analysis: fluid around the lungs
These tests are done to help
doctors stage lymphoma after it has been diagnosed. Staging is done to
determine how far tumors may have spread. Generally, tumors that are localized
to one site are less serious than those that have disseminated (spread) to
other tissues or organs.
A pathologist (physician
trained to identify cancer cells) or hematologist (specialist in blood
disorders) can tell a great deal about a given sample by examining the cells
under a microscope. He or she will look for abnormalities in shape, size,
appearance, and arrangement and may be able to diagnose the type of lymphoma
outright. Other tests or methodologies may be required, however, to make
specific diagnoses. These include immunohistochemistry,
which uses antibodies and staining techniques to differentiate among the many
types of lymphoma, flow cytometry, cytogenetics and molecular genetic studies.
Other tests that may help
diagnose the extent of a patient’s disease—by identifying the locations of
tumors and affected organs—may include imaging studies, such as chest X-rays
and CT scans, ultrasound scans, magnetic resonance imaging (MRI), positron
emission tomography (PET) scans, gallium scans, and bone scans.
Ultrasound scans use high-frequency
sound waves and their echoes to form an image of internal organs and
structures. Gallium scans, performed in a hospital nuclear medicine department,
involve injection of a small amount of the radioactive element gallium into a
vein. In time the element concentrates in lymphatic tissue. After one or two
days the patient returns to be scanned with an instrument that is sensitive to
minute amounts of radiation.
Although PET scans have largely
replaced this older technique, the gallium scan may still be used to identify
small tumors that PET scans might miss. It may also be used to differentiate
between lymph tissue abnormalities caused by infection and those caused by
lymphoma, in cases where diagnosis remains unclear.
A bone scan (which should not
be confused with a bone density scan, used to diagnose osteoporosis) helps
identify areas of bone that may have been damaged by lymphoma. A small amount
of the radioactive element technetium is injected into a patient’s vein. The
element travels to bone cells and emits gamma rays, which can be imaged using
an instrument known as a gamma camera. This scan is performed the same day as
the injection of the radioactive tracer substance.
Although not used to diagnose
lymphoma, certain blood tests may be ordered after a lymphoma diagnosis to
assess the status of organs, such as the liver and kidneys, or to determine how
advanced the disease is. Blood tests may also be necessary to determine the
levels of certain minerals, which may require adjustment.