Blood cancer develops when DNA in blood-forming cells becomes damaged, causing those cells to grow uncontrollably instead of maturing into normal blood cells. There is no single cause. Most cases result from a combination of acquired genetic mutations, environmental exposures, and sometimes inherited predispositions. The three main types are leukemia, lymphoma, and myeloma, and each has a slightly different origin story, but the underlying theme is the same: something goes wrong in the DNA of cells that produce or regulate your blood.
How Blood Cells Become Cancerous
Your bone marrow produces billions of new blood cells every day from a small pool of stem cells. Each time those stem cells divide, there’s a chance for errors in DNA copying. Most errors are harmless or get repaired. But when mutations hit genes that control cell growth, like the tumor suppressor gene TP53, cells can begin dividing without the usual brakes. Over time, one mutant cell can spawn a growing population of abnormal cells that crowd out healthy ones.
This process rarely happens in a single step. Research tracking how leukemia develops has shown that mutations accumulate in waves. An early “founding” clone might carry mutations in a dozen or more genes, and over months or years, new subclones branch off with additional mutations in cancer-driving genes. By the time the disease becomes detectable, the cancer has often evolved through several generations of increasingly aggressive cells. This is why blood cancers are most common later in life: the median age at leukemia diagnosis is 68, reflecting decades of accumulated DNA damage.
Chemical and Environmental Exposures
Benzene is the most well-established chemical cause of blood cancer, particularly leukemia. It’s found in gasoline, industrial solvents, cigarette smoke, and certain manufacturing processes. Workers with long-term occupational benzene exposure face dramatically elevated risk. One major study of industrial workers found that 45 years of exposure at an average concentration of 10 parts per million could result in 44 to 152 excess leukemia deaths per 1,000 workers. Even at lower levels, the relationship between benzene and leukemia follows a pattern where more exposure means more risk, with no clear safe threshold.
Pesticides, formaldehyde, and certain herbicides have also been linked to increased blood cancer risk, particularly non-Hodgkin lymphoma. For most people, everyday exposure to these chemicals is far below occupational levels, but the connection underscores why workplace safety regulations matter for those in industries like petroleum refining, rubber manufacturing, and chemical production.
Radiation Exposure
Ionizing radiation damages DNA directly, and blood-forming cells in the bone marrow are especially vulnerable because they divide so frequently. A large international study following nearly 310,000 nuclear industry workers for an average of 35 years found that leukemia death rates increased by more than 250% per gray of radiation absorbed. Even at the low doses typical in the study (around 0.016 gray on average), researchers estimated 13 excess leukemia deaths per 100,000 workers over 35 years.
These findings align closely with data from Japanese atomic bomb survivors, where the excess leukemia rate was 2.75 per gray. For context, a single CT scan delivers roughly 0.01 to 0.03 gray. One scan is not a meaningful risk, but repeated medical imaging over a lifetime does add up. Radiation therapy for a previous cancer delivers far higher doses to targeted areas and carries a more significant risk of secondary blood cancer.
Prior Cancer Treatment
One of the more unsettling causes of blood cancer is treatment for a previous, unrelated cancer. Certain classes of chemotherapy drugs can damage the DNA of healthy bone marrow cells while killing tumor cells elsewhere. The resulting “treatment-related” leukemia typically appears years later.
The timeline depends on the type of treatment. Alkylating agents, a common category of chemotherapy, tend to cause leukemia 5 to 7 years after treatment, often preceded by a phase where the bone marrow produces abnormal cells that aren’t yet fully cancerous. Another class of drugs called topoisomerase inhibitors has a shorter latency of 2 to 3 years. In some cases, though, the gap can be much longer. A study of childhood cancer survivors found secondary leukemias developing with a mean latency of nearly 22 years, with some cases appearing more than 30 years after the original treatment. Radiation therapy, particularly when it targets areas near large bones (where marrow is concentrated), adds to this risk.
Inherited Genetic Conditions
Most blood cancers are not directly inherited, but certain genetic conditions significantly raise the odds. These inherited syndromes don’t guarantee cancer, but they create a vulnerable starting point where fewer additional mutations are needed to trigger disease.
Fanconi anemia is one of the best-known examples. Caused by mutations in any of at least 21 different genes involved in DNA repair, it leaves cells unable to fix damage efficiently, making leukemia far more likely. Shwachman-Diamond syndrome, another inherited bone marrow failure condition, predisposes to leukemia through a similar mechanism. In both conditions, TP53 mutations frequently appear as the disease progresses toward cancer.
Other inherited syndromes span a wide range:
- Li-Fraumeni syndrome (caused by TP53 mutations) raises risk for many cancers including lymphoma
- Lynch syndrome (caused by mismatch repair gene mutations) is best known for colon cancer but also increases blood cancer risk
- Down syndrome (trisomy 21) substantially increases the risk of childhood leukemia
- Ataxia telangiectasia (caused by ATM gene mutations) impairs DNA damage responses and raises lymphoma risk
- GATA2 deficiency syndrome predisposes to myeloid leukemias beginning in adolescence or young adulthood
Familial clustering of blood cancers can also occur without a recognized syndrome. Mutations in genes like DDX41 and RUNX1 can run in families and predispose multiple generations to leukemia, sometimes without any other obvious symptoms beforehand.
Viruses and Infections
A small but important fraction of blood cancers are triggered by viral infections. The Epstein-Barr virus (EBV), which causes mono and infects the vast majority of adults worldwide, is linked to certain types of lymphoma, particularly Burkitt lymphoma and some forms of Hodgkin lymphoma. The virus persists in immune cells for life, and in rare circumstances, the viral DNA disrupts normal cell growth controls.
Human T-cell lymphotropic virus type 1 (HTLV-1) causes adult T-cell leukemia/lymphoma, though this virus is geographically concentrated in parts of Japan, the Caribbean, and Central Africa. Hepatitis C has been associated with certain non-Hodgkin lymphomas. HIV increases blood cancer risk primarily by suppressing the immune system, which normally keeps potentially cancerous cells in check.
Obesity and Chronic Inflammation
Carrying excess body weight increases the risk of multiple myeloma and possibly other blood cancers through several interconnected pathways. Fat tissue is not passive storage. It actively secretes signaling molecules called adipokines that can promote cancer cell growth. Lab studies have shown that bone marrow fat cells directly stimulate myeloma cells to proliferate and adhere more effectively, essentially feeding the cancer.
Obesity also drives insulin resistance, elevated growth factor levels, higher oxidative stress, and a state of chronic low-grade inflammation. Each of these creates conditions where cancerous cells are more likely to survive and thrive. The altered mix of signaling molecules from excess fat tissue can activate growth pathways in blood cells that would normally stay switched off.
Age and Accumulated Damage
The single biggest risk factor for most blood cancers is simply getting older. As stem cells in your bone marrow divide over decades, mutations inevitably accumulate. By age 70, many otherwise healthy people carry small populations of blood cells with cancer-associated mutations, a condition called clonal hematopoiesis. Most of these people never develop blood cancer, but the condition represents a measurable increase in risk.
This age-related accumulation of mutations explains why childhood blood cancers (which are more often driven by inherited conditions or specific chromosomal rearrangements) look biologically different from blood cancers diagnosed in older adults. In children, a single dramatic genetic event can be enough. In adults, blood cancer is typically the end result of a slow, multi-step process spanning years or decades, with each new mutation pushing cells a little further from normal behavior.