Non-Hodgkin lymphoma is not leukemia, but the two cancers are closely related. Both arise from the same type of blood cell, and in some cases the line between them blurs so much that a single disease can be classified as either one depending on where it shows up in the body.
Where Each Cancer Starts
Both non-Hodgkin lymphoma (NHL) and leukemia are cancers of white blood cells called lymphocytes, the immune cells responsible for long-term protection against infections. The key difference is location. Leukemia typically starts in the bone marrow and spreads through the bloodstream, flooding it with abnormal cells. Lymphoma usually starts in lymph nodes or the spleen and spreads through the lymphatic system, a separate network of vessels and tissues that filters fluid throughout the body.
This distinction in location also affects what the cancer physically looks like. Lymphoma cells can bind together and form solid tumors in lymph nodes or organs. Leukemia cells circulate freely in the blood and bone marrow without forming masses. That’s why lymphoma often presents as a painless lump or swelling, while leukemia is more likely to cause symptoms tied to bone marrow failure: unusual bruising, fatigue, frequent infections, or abnormal bleeding.
The Disease That Is Both
The strongest proof that these cancers aren’t entirely separate comes from a condition the medical world treats as a single disease with two names. Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) involve the exact same abnormal cell. According to the National Cancer Institute, the only difference is where those cells accumulate. If they’re found mostly in the blood and bone marrow, it’s called CLL. If they’re concentrated in the lymph nodes, it’s called SLL. Same biology, same treatment, different label based on where the cancer decides to set up shop.
This overlap exists because both cancers grow from lymphocytes, and the boundary between “blood cancer” and “lymph node cancer” was drawn before scientists fully understood the biology. The World Health Organization now classifies all of these diseases together under a single framework of blood and lymph tissue tumors, grouping them by cell type (B-cell or T-cell) rather than rigidly separating leukemia from lymphoma.
When Lymphoma Enters the Blood
Non-Hodgkin lymphoma can sometimes cross into territory that looks a lot like leukemia. This is called a “leukemic phase,” and it happens when lymphoma cells spill out of the lymph nodes and into the bloodstream in significant numbers. In one study of 214 NHL patients, about 14 percent developed a leukemic phase at some point during their illness.
How this plays out depends heavily on the type of lymphoma. In adult lymphoblastic lymphoma, a particularly aggressive subtype, leukemic conversion occurred in every patient studied. In diffuse large cell lymphomas, blood involvement typically appeared late in the disease as a sign that treatment was no longer working. The practical takeaway: a lymphoma diagnosis doesn’t guarantee the cancer stays out of the blood, and blood involvement doesn’t mean the original diagnosis was wrong.
How They’re Diagnosed Differently
Because the cancers occupy different parts of the body, the diagnostic process looks different. If a doctor suspects lymphoma, the starting point is usually a biopsy of an enlarged lymph node. A pathologist examines the tissue to identify the type of abnormal lymphocyte and how the cells are organized, which determines both the subtype and the likely behavior of the disease.
Leukemia, by contrast, is often caught first on a routine blood test that shows abnormal white blood cell counts. A bone marrow biopsy then confirms the diagnosis and identifies the specific type. That said, staging for lymphoma often includes a bone marrow biopsy too, precisely because doctors need to check whether the cancer has crossed into marrow territory.
Both Are B-Cell or T-Cell Cancers
Your immune system has two main types of lymphocytes. B cells produce antibodies to fight infections. T cells attack infected or abnormal cells directly. Both NHL and leukemia can arise from either cell type, which is part of why they share so much biology. B-cell lymphomas are the most common form of NHL. Lymphocytic leukemias also frequently involve B cells. When the same cell type goes wrong in the same way but in a different location, the resulting diseases naturally overlap.
This shared cellular origin is why treatments for certain lymphomas and leukemias use the same drugs. Therapies designed to target B cells, for example, work regardless of whether those B cells are sitting in a lymph node or circulating in the blood.
By the Numbers
Non-Hodgkin lymphoma is slightly more common than leukemia overall. An estimated 79,320 new NHL cases are expected in the United States in 2026, compared to 67,790 new leukemia cases. As of 2023, roughly 873,000 Americans were living with an NHL diagnosis. Both cancers span a wide range of subtypes with very different outcomes. Some are slow-growing and manageable for decades, while others are aggressive and require intensive treatment.
The distinction between NHL and leukemia matters for treatment planning, staging, and prognosis. But biologically, they sit on the same spectrum of blood cell cancers, and in certain cases they’re literally the same disease wearing a different name.