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.