Lymphoma originates in lymphocytes, the white blood cells that form the core of your immune system. These cells live throughout the lymphatic system, and lymphoma most often starts in lymph nodes found in the neck, armpits, groin, or gastrointestinal tract. But the full picture is more nuanced than that, because different types of lymphoma arise from different cells, at different stages of development, and sometimes in organs you wouldn’t expect.
The Cells Where Lymphoma Begins
Your body produces two main types of lymphocytes: B cells and T cells. B cells are born and mature in the bone marrow. T cells start in the bone marrow too, but travel to the thymus (a small gland behind the breastbone) to finish developing. A third, less common type called natural killer (NK) cells also belongs to this family. Lymphoma can arise from any of these three cell types.
The transformation from normal lymphocyte to cancer cell typically happens at a relatively late stage in a lymphocyte’s development, when the cell is already mature enough to recognize foreign invaders and respond to immune signals. At this point, the cell is actively reshuffling parts of its DNA to fine-tune its ability to target specific threats. That reshuffling process creates opportunities for genetic errors that can set a cell on the path toward uncontrolled growth.
Not all lymphomas follow this pattern, though. Some arise from very immature cells. Lymphoblastic lymphoma, for example, develops from precursor B cells still in the bone marrow or precursor T cells still maturing in the thymus. These are cells that haven’t yet finished their training. At the other end of the spectrum, peripheral T-cell lymphoma originates in fully mature T cells that have already left the thymus and taken up residence in lymph nodes or other tissues.
Hodgkin vs. Non-Hodgkin: Different Origins
The two broad categories of lymphoma are defined partly by which cells they come from. Hodgkin lymphoma arises from B cells, specifically from B cells that have passed through a structure called the germinal center, a specialized zone inside lymph nodes where B cells multiply and refine their immune responses. The hallmark of Hodgkin lymphoma is a distinctive abnormal cell called the Reed-Sternberg cell, visible under a microscope. These oversized cells are surrounded by a swarm of normal immune cells, which actually make up most of the tumor.
Non-Hodgkin lymphoma is a much broader group. It can originate from B cells, T cells, or NK cells. About 85% of non-Hodgkin lymphomas are B-cell types. Because these cancers can arise from lymphocytes at many different stages of development and in many different locations, non-Hodgkin lymphoma encompasses dozens of distinct diseases, each with its own behavior and outlook.
Where in the Body Lymphoma Starts
Most lymphomas begin in lymph nodes. You have hundreds of these bean-shaped structures clustered throughout your body, with the largest concentrations in your neck, armpits, chest, abdomen, and groin. Lymph nodes filter fluid and house large populations of lymphocytes, making them the most common starting point.
But lymphocytes don’t stay put. They circulate through your blood, lymphatic vessels, and tissues, which means lymphoma can also originate outside the lymph nodes entirely. These are called extranodal lymphomas, and they can start in almost any organ. The gastrointestinal tract is the most common extranodal site, with the stomach being the single most frequent location. After the GI tract, other common sites include the tonsils, lungs, liver, spleen, bone, and skin. Rarer locations include the brain (primary CNS lymphoma), kidneys, pancreas, and thyroid.
One well-studied example is MALT lymphoma, which develops in mucosa-associated lymphoid tissue. This is immune tissue that the body builds up in response to chronic infection or long-term inflammation. The stomach is the classic site: years of infection with the bacterium H. pylori can cause the stomach lining to accumulate immune cells that weren’t originally there. Over time, B cells in this acquired tissue can undergo clonal expansion and become cancerous. Because MALT tissue can form wherever there’s chronic irritation, MALT lymphoma can technically arise in almost any organ.
What Triggers the Transformation
A lymphocyte doesn’t become cancerous from a single event. It accumulates genetic damage over time, often through chromosomal translocations, where pieces of DNA break off and reattach in the wrong place. These rearrangements can activate genes that drive cell growth or disable genes that normally keep cell division in check.
Viruses play a direct role in some lymphomas. Epstein-Barr virus (EBV), the virus behind mono, is causally linked to at least five types of lymphoma, including Burkitt lymphoma, Hodgkin lymphoma, NK/T-cell lymphoma, diffuse large B-cell lymphoma, and primary effusion lymphoma. EBV infects B cells and pushes them to proliferate. Lab experiments have shown that B cells infected with EBV begin multiplying indefinitely, while uninfected cells die off. Specific viral proteins are essential for this initial transformation. Another virus, HTLV-1, infects mature T cells and is responsible for adult T-cell lymphoma, a disease seen primarily in regions where the virus is endemic.
Chronic immune stimulation, even without a virus, can also set the stage. Any condition that forces lymphocytes to divide repeatedly over months or years increases the chance of a DNA copying error that sticks. This is why autoimmune diseases, organ transplant medications that suppress the immune system, and chronic infections all raise lymphoma risk.
How Classification Reflects Origin
The way doctors classify lymphoma is built around the cell of origin. The most recent World Health Organization system organizes lymphomas hierarchically: first by whether they come from B cells or T/NK cells, then by whether the cell was mature or immature, and finally by specific genetic and microscopic features. Diffuse large B-cell lymphoma, the most common aggressive type, is further divided into subtypes based on whether the cancerous B cell resembles one that was actively passing through a germinal center or one that had already left it. These distinctions matter because they predict how the cancer will behave and which treatments are most likely to work.
Recent genetic profiling has revealed that even within a single lymphoma type, tumors can be driven by very different mutations. Diffuse large B-cell lymphoma, for instance, includes at least four distinct genetic subtypes, each defined by a different combination of mutations and chromosomal rearrangements. Some of these subtypes respond well to targeted therapies, while others do not. This means that two patients with the same diagnosis on paper may have cancers that originated through fundamentally different biological pathways.