Diagnosing Primary Central Nervous System Lymphoma

NYU Langone doctors diagnose primary central nervous system lymphoma, which is a rare form of non-Hodgkin lymphoma. This type of cancer starts in the body’s lymphatic system, which is composed of blood, tissue, and organs that help the body fight infection. It occurs when white blood cells called lymphocytes—which travel in and out of the central nervous system—become cancerous.

Although this cancer appears in the central nervous system, which consists of the brain and spinal cord, it may also be found in the meninges, which are the layers of tissue that protect the brain and spinal cord. Primary central nervous system lymphoma can also occur in the eye and is called ocular lymphoma.

People with weakened immune systems—including those who have human immunodeficiency virus (HIV) infection or acquired immunodeficiency syndrome (AIDS)—are at increased risk for lymphoma. Those who have had an organ transplant are also at greater risk, because they tend to have lower levels of infection-fighting blood cells.

In the past two decades, primary central nervous system lymphoma has become more common. It now accounts for 2 percent to 3 percent of all tumors that start in the brain.

Symptoms largely depend on the location of the tumor. People with brain tumors, for instance, may experience headaches, seizures, mental confusion, or nausea and vomiting. They may also have hearing loss, double vision, difficulty swallowing, and leg, arm, or facial weakness.

People who have tumors in the spinal cord or spinal fluid may experience back pain, leg weakness, and incontinence. Those who have ocular lymphoma may experience vision loss or blurry vision.

Diagnostic Tests

To diagnose primary central nervous system lymphoma, an NYU Langone doctor conducts a physical exam, in which he or she checks the lymph nodes for swelling. The doctor also asks about your symptoms and medical history to determine whether you have any risk factors for lymphoma, such as having had an organ transplant.

Next, your doctor may perform several diagnostic tests to identify the type of lymphoma and pinpoint how fast it is growing. These tests can determine how far the cancer has spread and how active it is. Tests may also help the doctor predict how well the cancer may respond to therapy and whether it might recur after treatment.

Blood Tests

Your doctor checks levels of red and white blood cells and platelets. People with primary central nervous system lymphoma often have anemia, or low levels of red blood cells, which carry oxygen to the body’s organs and tissues. They may also have low levels of platelets, which help the blood clot, as well as low levels of white blood cells, which fight infection.

These blood tests can help your doctor rule out leukemia, which starts in immature white blood cells found in the bone marrow.

HIV Test

HIV infection and AIDS are risk factors for primary central nervous system lymphoma. If your doctor suspects you have this cancer, he or she tests you for HIV, the virus that causes AIDS.

A standard blood test identifies HIV antibodies, proteins your body produces when it detects a harmful substance. It usually takes about 12 weeks for the body to develop detectable HIV antibodies after you’ve been infected. However, it can take up to six months for an HIV antibody test to become positive, depending on the test that’s used.

If a person tests positive for HIV infection, the doctor performs additional blood tests to estimate how long he or she has been infected and how far the virus has progressed. An HIV diagnosis may affect the type of treatment used for primary central nervous system lymphoma.

CD4 Count

CD4 cells, also known as T cells, are white blood cells that fight disease and infection. HIV invades CD4 cells and uses them to multiply and spread the virus throughout the body.

Blood tests can measure the number of healthy CD4 cells in a person’s blood. Very low CD4 levels may indicate that HIV infection has progressed to AIDS. People with AIDS-related lymphoma who have low CD4 levels do not fare as well as people who have a greater number of CD4 cells.

Neurological Exam

Because primary central nervous system lymphoma tumors can interfere with brain and spinal cord functioning, an NYU Langone doctor asks you a series of questions during a neurological exam. This helps the doctor check your cognitive ability.

He or she may ask what today’s date is and the name of the country. The doctor may also perform abstract thinking tests, in which you are asked to interpret common sayings. Or, you may be given memory tests, in which you are asked to repeat a list of objects. Our specialist may also test your reflexes, strength, coordination, and ability to walk.

Imaging Tests

Doctors use imaging tests to diagnose primary central nervous system lymphoma and to determine if cancerous cells have spread to other parts of the brain and spinal cord. These tumors don’t usually spread to other parts of the body.

MRI Scans

An MRI scan uses a magnetic field and radio waves to create computerized, three-dimensional images of structures in the body. MRIs are better at highlighting the soft tissue of the brain than other types of imaging tests.

CT Scans

This test can help your doctor determine the location and size of lymphoma tumors. A CT scan uses X-rays and a computer to create three-dimensional, cross-sectional images of the body.

Prior to the scan, your doctor may give you a contrast agent, or dye, by mouth or as an injection into a vein. The agent travels throughout the body, highlighting organs and blood vessels. The contrast fluid is iodine-based, so this test is not recommended for anyone who has a seafood or iodine allergy.

PET Scans

Your doctor may use a PET scan to determine how aggressive the cancer is. A PET scan involves injecting a small amount of radioactive glucose, or sugar, into a vein. This substance collects in tumor cells, which are detected by a computer during the scan. The computer creates three-dimensional images of cancer activity in your body.

Because cancerous cells process glucose more rapidly than healthy cells, the former appear brighter on PET scans.

Sometimes, a PET scan and CT scan are done at the same time. This PET/CT scan provides a more complete picture of what is happening in the body than either test can provide on its own.

Stereotactic Biopsy

If an imaging test reveals a tumor in the brain, your doctor may recommend a stereotactic biopsy, a surgical procedure in which a small amount of tissue is removed for examination under a microscope.

The doctor uses a MRI or CT scan to create a three-dimensional view of the brain, which helps him or her map the exact location and dimensions of the tumor.

A local anesthetic is applied to the skull, where the surgeon makes a small incision. He or she inserts a thin needle and advances it to the tumor, using MRI or CT images for guidance. Then the surgeon removes tissue samples and sends them to a laboratory, where a pathologist studies them under a microscope.

The pathologist may perform one or more tests on the tissue samples.

Chromosome Analysis

Chromosomes are the parts of a person’s cells that carry genetic information. The presence of atypical chromosomes and genetic mutations, or changes, helps your doctor determine the type of lymphoma you have and choose the appropriate treatment.

During a chromosome analysis, the doctor checks tumor cells for certain chromosomal changes that occur when cells become cancerous. Your doctor may use a newer test called fluorescence in situ hybridization, which can detect chromosomal changes that conventional chromosomal analysis can’t.

Flow Cytometry

With flow cytometry, our specialists study the size and shape of the cancer cells and look for tumor markers, which are substances in the blood that indicate you have a cancerous tumor. These tests help doctors differentiate lymphoma from leukemia and identify the type of lymphoma present in the body.

Immunohistochemistry

During an immunohistochemistry test, doctors examine cells in tissue for antigens, which are substances that cause the body’s immune system to attack other substances in the body. Because specific antigens are found on cancer cells, this test can help determine the type of cancer you have and how aggressive it is. This test is used to differentiate primary central nervous system lymphoma from other brain tumors, such as gliomas.

Lumbar Puncture

Primary central nervous system lymphoma can spread to the fluid that surrounds the spine and brain. This is called the cerebrospinal fluid. To determine if this has occurred, a doctor may perform a lumbar puncture, also known as a spinal tap.

This test involves inserting a needle into the spinal canal through the lower back and withdrawing a sample of cerebrospinal fluid to determine if lymphoma cells are present. Doctors use local anesthesia for this procedure.

Slit-Lamp Eye Exam

If your doctor suspects that the cancer has spread to the eyes, a slit-lamp eye exam is performed. During this test, an eye specialist, or ophthalmologist, uses a microscope that shines a thin beam of light to examine the inside of your eyes for signs of cancer.

During the test, your eyes are dilated with drops to widen your pupils, making it easier for the doctor to see inside the eye. A camera attached to the microscope allows the doctor to take pictures of different parts of the eye.

Sometimes, a vitreous biopsy is performed to extract tissue from inside the eye for examination under a microscope. Doctors typically use a local anesthesia to perform this procedure. They insert a thin needle into the vitreous, the transparent substance that fills the center of the eye, to obtain a sample of tissue to test for ocular lymphoma.