The core cause: DNA damage in lymphocytes

Lymphoma develops when lymphocytes—a type of white blood cell—accumulate genetic mutations that cause them to multiply uncontrollably. These mutations happen in the cell's DNA and prevent the normal signals that tell cells when to stop dividing or die. The result is a population of abnormal cells that crowds out healthy ones, forming tumors in lymph nodes, the spleen, bone marrow, or other organs.

The mutations are not inherited from a parent in most cases. Instead, they occur randomly in a single cell during a person's lifetime, then that cell divides repeatedly, passing the mutation to its descendants. This is why lymphoma is not contagious and why it does not run in families in the way that some genetic conditions do.

Scientists do not yet fully understand why these mutations happen in some people and not others. The process appears to involve both random chance and exposure to certain risk factors that make mutations more likely.

Key Takeaways

  • Lymphoma starts when a lymphocyte develops a DNA mutation that causes it to divide without stopping, crowding out healthy cells.
  • These mutations occur randomly during a person's lifetime and are not inherited from parents or passed between people.
  • Risk factors including age, immune system weakness, certain infections, and autoimmune conditions increase the chance that mutations will develop.
  • Exposure to pesticides, solvents, or radiation may raise risk, though the evidence is stronger for some exposures than others.
  • Most people with risk factors never develop lymphoma, and many people who develop it have no known risk factors.

Age and immune system changes

Lymphoma becomes more common as people age. The median age at diagnosis is in the 60s for most types, though some forms occur in younger adults and children. One reason is that the immune system changes over decades—cells accumulate more mutations simply because they have been dividing longer, and the body's ability to repair DNA damage or eliminate abnormal cells declines.

People with weakened immune systems face higher risk. This includes people living with HIV, those taking immunosuppressive medications after an organ transplant, and people with certain inherited immune disorders. When the immune system cannot monitor and eliminate abnormal cells effectively, mutated lymphocytes are more likely to survive and multiply.

Infections that increase risk

Certain viral and bacterial infections are linked to lymphoma development. Epstein-Barr virus (EBV) is associated with some types of Hodgkin lymphoma and certain non-Hodgkin lymphomas, particularly in people with weakened immunity. Human T-cell leukemia virus type 1 (HTLV-1) causes a rare aggressive lymphoma and is transmitted through blood transfusion, sexual contact, or breast milk in areas where it is endemic.

Hepatitis C virus is linked to certain lymphomas, especially in the liver and lymph nodes. Human herpesvirus 8 (HHV-8) is associated with a type of lymphoma that occurs mainly in people with advanced HIV. Helicobacter pylori, a bacterium that causes stomach ulcers, is linked to a rare lymphoma of the stomach lining.

Having one of these infections does not mean a person will develop lymphoma. Most infected people never do. The infection appears to create conditions—chronic inflammation, immune activation, or direct damage to lymphocytes—that make lymphoma more likely over time.

Autoimmune conditions and chronic inflammation

People with autoimmune diseases face modestly higher lymphoma risk. Conditions including rheumatoid arthritis, lupus, Sjögren's syndrome, and celiac disease are associated with increased rates. The connection appears to involve chronic immune activation: when the immune system is constantly fighting the body's own tissues, lymphocytes are stimulated to divide repeatedly, raising the odds that a mutation will occur in one of those divisions.

The increased risk is real but not large. Most people with autoimmune disease do not develop lymphoma, and the absolute number of cases remains uncommon. Some medications used to treat autoimmune conditions may also contribute to risk, though separating the effect of the disease itself from the effect of treatment is difficult.

Environmental and occupational exposures

Exposure to certain chemicals has been studied as a possible cause. Pesticides and solvents used in agriculture, manufacturing, and cleaning have been associated with lymphoma in some research, though the evidence is not conclusive and varies by specific chemical and type of lymphoma. People in farming, painting, and chemical manufacturing have been studied most closely.

Radiation exposure is a clearer risk factor. People exposed to high doses during medical treatment (such as radiation therapy for another cancer) or occupational exposure face higher risk. The atomic bomb survivors in Japan showed increased lymphoma rates decades after exposure. Low-level environmental radiation from natural sources does not appear to raise risk meaningfully.

The challenge with environmental causes is that lymphoma is relatively uncommon, so it is difficult to prove that a specific exposure caused a specific case. Many people are exposed to pesticides or solvents without developing lymphoma, and many people with lymphoma have no known exposure history.

Obesity and hormonal factors

Obesity is associated with increased lymphoma risk, particularly for non-Hodgkin lymphoma. The mechanism is not fully clear but may involve chronic inflammation, changes in hormone levels, or effects on immune cell function. The increased risk is modest and appears to be stronger in women than men.

Hormone use, particularly estrogen-containing medications, has been studied as a possible risk factor with mixed results. Some studies suggest a small increase in risk with long-term use, while others find no association. The evidence is not strong enough to recommend avoiding hormone therapy based on lymphoma risk alone, but it is one factor to discuss with a doctor when weighing the benefits and risks of treatment.

Genetic predisposition and family history

While lymphoma itself is not inherited, some families carry genetic variations that make lymphoma more likely. These are not mutations that cause lymphoma directly but rather variations in genes involved in immune function or DNA repair. People with a first-degree relative (parent, sibling, or child) who had lymphoma have a modestly higher risk than the general population, though most will never develop the disease.

Certain inherited conditions that affect the immune system, such as ataxia-telangiectasia or Wiskott-Aldrich syndrome, carry substantially higher lymphoma risk. These are rare conditions, and genetic testing is not recommended for the general population based on lymphoma risk alone.

Frequently Asked Questions

Can you catch lymphoma from someone who has it?

No. Lymphoma is not contagious and cannot be transmitted from one person to another through contact, blood, or any other means. The mutations that cause it occur in a single person's cells and are not passed to others.

If my parent had lymphoma, will I definitely get it?

No. Having a family member with lymphoma increases your risk slightly compared to someone with no family history, but most people with a family history never develop lymphoma. The increased risk is modest, and most cases occur in people with no family history at all.

Does stress cause lymphoma?

There is no strong evidence that stress directly causes lymphoma. Chronic stress may affect immune function over time, but this has not been proven to cause lymphoma in humans. Many people experience significant stress without developing lymphoma.

Are cell phones or power lines linked to lymphoma?

Large studies have not found evidence that radiofrequency radiation from cell phones or extremely low-frequency radiation from power lines causes lymphoma. These remain areas of ongoing research, but current evidence does not support a causal link.

What should I do if I have multiple risk factors?

Having risk factors does not mean you will develop lymphoma. Most people with risk factors never do. There is no proven way to prevent lymphoma, so the best approach is to maintain overall health through regular exercise, a balanced diet, and routine medical checkups. Talk with your doctor about your specific risk factors if you have concerns.