Physicians use several kinds of tests to diagnose non-Hodgkin's lymphoma. These tests help determine the exact type of lymphoma and to uncover other features that are helpful in deciding on the most effective course of treatment.
Biopsy
During a biopsy, physicians remove a small amount of tissue for analysis. There are several types of biopsies, including the following:
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Excisional or incisional biopsy
The physician cuts through the skin to remove an entire lymph node (excisional) or a small piece of cancerous tissue (incisional). Biopsy is considered the gold standard for the diagnosis of non-Hodgkin's lymphoma.
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Fine-needle aspiration biopsy
The physician draws tissue from a tumor into a syringe.
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Bone marrow biopsy and aspiration
The physician withdraws a small sample of bone marrow through a needle. This test is most useful in determining if non-Hodgkin's lymphoma has spread to the bone marrow.
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Lumbar puncture (also called a spinal tap)
The physician removes cerebrospinal fluid from the spinal cavity in the lower back. This test is generally used to determine the extent of disease in patients at high risk of spinal fluid involvement.
Imaging
Physicians use imaging tests to determine the location of tumors in the body. Here are a few examples:
- Chest x-rays can detect tumors in the chest and lungs.
- Using computed tomography (CT), physicians can take pictures of the body from a number of angles; these pictures are then combined to produce detailed images of the inside of the body.
- Magnetic resonance imaging (MRI) uses magnets and radio waves to produce detailed pictures of soft tissues and organs.
- In gallium scans and positron emission tomography scans using fluorodeoxyglucose (FDG-PET), a radioactive substance is injected into the body and migrates to cancerous sites. Using a special camera, physicians can see where the radioactive material collects, and determine the extent of the spread of disease.
Cell Studies
In addition, physicians can use a number of tests that help them determine specific features of the cells in biopsied tissue including genetic abnormalities such as chromosomal rearrangements, which are common in lymphomas, and whether the cells have receptors for specific antigens (which helps both identify the cells' origins and determine the patient's prognosis). These tests include:
- immunohistochemistry studies, in which antibodies are used to distinguish between types of cancer cells
- cytogenetic studies to determine chromosome changes in cells
- flow cytometry, in which prepared cells are passed through a laser beam for analysis
- molecular genetic studies (highly sensitive DNA and RNA tests to determine specific genetic traits of cancer cells)
New diagnostic tests and procedures are emerging from work on the human genome and gene expression analysis; these are likely to be important in the future but are currently experimental.
