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Primary central nervous system (CNS) lymphoma

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was reviewed on May 31, 2022.

Primary central nervous system lymphoma is a type of non-Hodgkin lymphoma that starts in the central nervous system (CNS). CNS lymphoma can form in the:

  • Brain
  • Spinal cord
  • Layers of tissue that protect the brain and spinal cord (meninges)
  • Eye (called primary intraocular lymphoma)

Together, the brain and spinal cord make up the CNS, which is responsible for coordinating and controlling nearly everything your body does. Primary CNS lymphoma most often develops in the brain, but also sometimes forms in the eye because it’s very close to the brain. Wherever primary CNS lymphoma begins, it tends to spread throughout the CNS over time.

Lymphoma is a cancer of the lymphatic system, which is part of the immune system that helps your body fight infections. This network of lymph nodes, organs and tissue make and carry immune system cells called lymphocytes throughout the body. These cells travel in a fluid called lymph, similar to how the circulatory system transports blood.

Doctors aren’t sure exactly how primary CNS lymphoma starts. It happens more often in adults between the ages of 45 and 70, though it can develop at any age. Having a compromised immune system may put you at higher risk for developing primary CNS lymphoma.

Primary CNS lymphoma is a rare type of cancer. Nearly 1,500 new cases are diagnosed in the United States each year, according to the U.S. National Library of Medicine.

Causes and risk factors of CNS lymphoma

Lymphoma starts in immune system cells called lymphocytes. There are two main types of lymphocytes: B cells and T cells. Most lymphomas affect B cells, and the same goes for primary CNS lymphoma. Lymphoma occurs when these cells develop mutations that cause them to divide and multiply out of control.

Doctors don’t yet understand what causes lymphoma cells to form in the brain or spinal cord. They’re not sure whether lymphocytes enter the CNS and become malignant or the cells are already malignant by the time they arrive.

Although the exact causes of primary CNS lymphoma remain unknown, some things may increase the risk of developing the cancer. Risk factors for primary CNS lymphoma include:

A weakened immune system: Being immunocompromised or having poor immune system function increases the risk of developing primary CNS lymphoma. Common causes of weakened immunity include having HIV/AIDS (especially if untreated) or taking drugs to suppress the immune system after an organ transplant. Being infected with the Epstein-Barr virus (EBV) has also been linked to primary CNS lymphoma, especially in people who have HIV/AIDS.

Age: Most cases of primary CNS lymphoma are diagnosed in people around age 60. People who are immunocompromised tend to develop the disease earlier, around age 45. However, there are rare reports of primary CNS lymphoma in children.

Symptoms of CNS lymphoma

The signs and symptoms of primary CNS lymphoma may be different depending on where the cancer starts. Symptoms tend to develop relatively quickly and get worse over a matter of weeks. Potential signs of primary CNS lymphoma may include:

  • Problems with balance and coordination
  • Weakness in arms or legs
  • Changes in behavior, personality and the ability to speak
  • Headaches, vomiting and vision changes
  • Seizures
  • Loss of bladder and bowel control
  • Confusion
  • Hearing loss

Other symptoms depend on the part of the brain where the tumor is located. For example, overeating, having a decreased sex drive, being very thirstyt and having to urinate often are potential signs that the pituitary gland or hypothalamus have been damaged.

If primary CNS lymphoma invades the bottom of the brain that connects to the spinal cord (the brain stem), patients may have trouble with their balance, or they may experience vertigo, changes in eye movements and persistent vomiting.

Primary CNS lymphoma rarely affects the spinal cord. If this does occur, symptoms may include:

  • Generalized weakness
  • Inability to feel or move parts of the body
  • Changes in bladder and bowel control

Primary CNS lymphoma often spreads to the eye. In about 20 to 40 percent of cases, the cancer has already invaded the eye by the time it’s diagnosed, according to the National Organization for Rare Disorders. Symptoms of primary CNS lymphoma in the eye include blurred vision and seeing small, dark shapes (floaters).

Diagnosing CNS lymphoma

People who have primary CNS lymphoma are often diagnosed after they being experiencing symptoms. Your doctor will likely start by evaluating your symptoms and asking questions about your medical history. He or she will examine you and perform a neurological exam to check the function of your brain and spinal cord. You’ll also answer questions and perform tests to check your memory, cognition, coordination, balance and reflexes.

If your doctor thinks you may have a CNS tumor, you also may under go the following tests:

Eye exam: The doctor will give you eye drops to widen your pupil, enabling the doctor to see all of your eye, including the retina (which is at the back of the eye). Then, the doctor will use a machine with a microscope or a magnifying lens to look inside the eye.

Imaging tests: Imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) scans take detailed images of the brain and, if needed, the spinal cord. These pictures can help show any abnormalities in the central nervous system, such as a tumor.

Biopsy: To be certain about the diagnosis, your doctor will perform a biopsy, usually by using a lumbar puncture. A lumbar puncture, also called a spinal tap, involves inserting a thin needle into your lower back and collecting a sample of cerebrospinal fluid (CSF). Pathologists, who are experts in diagnosing diseases, will look for cancerous cells in the fluid. In some cases, if no cancerous cells are found, you may need to undergo a stereotactic biopsy. For this procedure, a neurosurgeon will use a 3D scanner and a computer to locate the tumor so he or she can take a tissue sample.

Blood tests: While blood tests can’t diagnose primary CNS lymphoma, they often provide additional information. For example, your blood may be tested for HIV. You also may undergo a test called a complete blood count (CBC) to measure levels of different types of cells in the blood, which may change when you have primary CNS lymphoma. Other blood tests may be used to determine levels of specific substances in the blood, such as lactate dehydrogenase (LDH), which may help indicate the severity of the disease.

Treating CNS lymphoma

When recommending a treatment plan, your care team will consider many factors, including:

  • The cancer’s location
  • Your age
  • Your overall health
  • Your personal preferences

Most patients with primary CNS lymphoma receive chemotherapy, either by itself or with radiation therapy.

Chemotherapy treats cancer using drugs that kill or damage cancer cells. The drugs must usually be given at high doses so they can more easily enter the brain and target cancer cells. Chemotherapy drugs may be delivered in several ways:

  • Injected into a vein or muscle
  • Placed directly into the brain cavities or cerebrospinal fluid
  • Injected into the eye (for primary intraocular lymphoma)

How chemotherapy is delivered depends on the location of the tumor and other factors.

Radiation therapy treats cancer with beams of energy that are targeted at the area of cancer. For primary CNS lymphoma, radiation is targeted at the entire brain, since the cancer is often widespread. Because using radiation on the brain may cause cognitive changes, doctors use this option cautiously, particularly in older people. Older patients, or those with poor overall health, may receive lower doses of chemotherapy or radiation therapy.

A stem cell transplant may be an option for certain patients, particularly those who are young and otherwise healthy. This involves extracting stem cells (immature blood cells) from the blood or bone marrow and then storing them while the patient undergoes high-dose chemotherapy treatment. After the chemotherapy is delivered, doctors put the stem cells back in the patient’s body. A patient who has a stem cell transplant may receive more intense chemotherapy, which often damages blood cells. Your care team can help you determine whether this treatment is right for you.

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