5 Major Differences between Leukemia and Lymphoma
You may have noticed that there is a lot of information as well as organizations which lump leukemia and lymphoma together. What are the differences and what are the similarities between leukemias and lymphomas?
Differences between Leukemias and Lymphomas
Leukemias and lymphomas are often grouped together. The reason this is so is that they are both considered “blood-related” cancers. This is in contrast to “solid tumors” such as breast cancer or lung cancer.
We will discuss some of these differences ranging from definitions and origin to cells, but it’s important to note right away that there are exceptions. There are many differences within the group of cancers called leukemias as well as among diseases classified as lymphomas. In fact, you will note that sometimes one of the characteristics of leukemia is more common in one type of lymphoma than in some leukemias, and vice versa. An example is when we talk about differences in the age at which these cancers occur. Leukemia is the most common childhood cancer, and we often think of leukemias as childhood diseases and lymphomas as cancers which occur in older adults. Yet many types of leukemia are more common in older adults, while some types of lymphoma, such as Hodgkin’s lymphoma, are frequently found in young people.
Realizing that there is much overlap and many exceptions, let’s take a look at the most common differences between leukemias and lymphomas.
Leukemia and lymphoma are defined in a way that may seem odd by today’s standards, with many exceptions and overlapping concepts. This is in part because these definitions were developed long ago, starting in the 1800s. Here are two key differences in the definitions, to start out with:
- One key item to pay attention to is whether or not the malignancy is typically associated with high numbers of white blood cells, or leukocytes, circulating in the peripheral circulation, or the bloodstream. Both red and white blood cells are formed inside certain bones of the body, in the bone marrow, and “peripheral blood” describes those cells that have made it out of the blood vessels and are no longer in the marrow. This excess of white blood cells in the peripheral bloodstream is more typical of leukemia.
- Another key thing to know about is whether the disease develops with early involvement of the bone marrow, which is also more typical of leukemia.
Now, let’s examine the medical terms actually used to define leukemia and lymphoma.
- Lymphoma is defined as “any malignancy of the lymphoid tissue.” So, what’s the lymphoid tissue, you ask? The lymphoid tissue includes both cells and organs. Cells—including some white blood cells—and organs—including the thymus, bone marrow, lymph nodes, and spleen. The most common cell type in the lymphoid tissue is the lymphocyte. In addition to organs, lymphoid tissue also includes collections of cells located throughout the body, at strategic sites to fight off invaders. Examples of these sites include the tonsils, areas in the respiratory tract, beneath moist mucous membranes, such as those of the gastrointestinal tract, and other tissues of the body.
- Leukemia is defined as “a progressive, malignant disease of the blood-forming organs, characterized by distorted proliferation and development of leukocytes and their precursors in the blood and bone marrow.” So, what are the blood-forming organs, you ask? In adults, the bone marrow produces all of the red blood cells, most of the white blood cells called granulocytes. While lymphocyte development starts in the bone marrow, they migrate to the lymphoid tissues, and especially the thymus, the spleen, and the lymph nodes, and these tissues play a vital role in the development and maturation of the lymphocytes. (There are differences between B lymphocytes (B cells) and T lymphocytes (T cells) but for the purposes of this discussion we won’t cover that here.) Special tissues of the spleen, liver, lymph nodes and other organs are likewise important in the maturation of monocytes.
Leukemia and lymphoma are not diagnosed based on symptoms alone; many symptoms overlap or are not specific to either disease, while some other symptoms may be more characteristic of one disease or the other.
Symptoms of lymphoma vary and may include painless swelling of lymph nodes. These lymph nodes may be visible in your neck, armpits, or groin, or may instead be seen on imaging studies (such as mediastinal nodes, retroperitoneal nodes, and more.) Other symptoms may include persistent fatigue, fever, and chills, night sweats or unexplained weight loss.
The most common types of leukemia can produce symptoms such as bone and joint pain, fatigue, weakness, pale skin (due to low levels of red blood cells, known as anemia,) easy bleeding or bruising (due to a low levels of platelets, or thrombocytopenia,) fever, weight loss, and other symptoms, including swollen lymph nodes, spleen, and liver.
People with lymphomas may have symptoms referred to B symptoms, which often indicate a more aggressive or faster-growing cancer. B symptoms of lymphoma include fevers, unintentional weight loss, and drenching night sweats,
Differing Cell Types of Origin and Cells in the Circulation
Describing the different types of cells and origin of cancers between leukemias and lymphomas is easiest by describing a few specific types of these diseases.
Types of Leukemia
There are four basic types of leukemia.
Here are the first two:
1. Acute myeloid leukemia, or AML
2. Chronic myeloid leukemia, or CML
As these names suggest, two types of leukemia are “myeloid,” which means “of or like the bone marrow,” which makes sense, since bone marrow is the body’s factory for making white blood cells. But the word myeloid also refers to the group of cells that differentiate, or grow up, from one common ancestor—a myeloid progenitor cell. So, because of that ‘myeloid’ in the name, we are referring to cells of the blood-forming tissues that hail from the same part of the family tree of white blood cells.
Now look at the second two leukemia types:
3. Acute lymphocytic leukemia, or ALL
4. Chronic lymphocytic leukemia, or CLL
Now, with ALL and CLL, it may seem like we are in a bit of trouble with our definitions.
The second two kinds of leukemia derive from lymphocyte lineage.
Technically, ALL and CLL should be lymphomas, then, right?—they are lymphocytic—and lymphocytes are a cell type that is a part of the lymphoid tissue. Well, not quite. Though the lymphocytes are key cells in lymphoid tissue, they start out in the bone marrow and migrate to the lymphoid tissue. Additionally, it’s now time to go back to that nagging clause in the definition of leukemia: “…characterized by distorted proliferation and development of leukocytes and their precursors in the blood and bone marrow.”
The proliferation, or growth and multiplication, of white blood cells and their precursors in the bone marrow—and presence in the blood—is a part of the leukemia definition that serves to distinguish many leukemias from many lymphomas.
Types of Lymphoma
Here are the 2 basic types of lymphoma:
1. Hodgkin’s lymphoma, or HL
2. Non-Hodgkin’s lymphoma, or NHL
A large variety of cancers derive from lymphocytes or their precursors—these lymphoma cells will usually not appear in the peripheral blood, which means that they can’t be properly called leukemias.
**There are exceptions. Also, some malignancies have features characteristic of both leukemia and lymphoma.
Differences in Incidence
There are differences in the incidence, or how often leukemias and lymphomas occur, as well. Overall, more people develop lymphomas than leukemias.
Here are the American Cancer Society’s estimates for new cases in 2017 broken down by subtypes:
Lymphoma: 80,500 people
- 72,240 non-Hodgkin’s lymphoma
- 8,260 Hodgkin’s lymphoma
Leukemia: 62,130 people
- 21,380 acute myeloid leukemia
- 6,660 chronic myeloid leukemia
- 5,970 acute lymphocytic leukemia
- 20,110 chronic lymphocytic leukemia
- 5,720 other leukemia
Differences in Age at Diagnosis
Leukemia is the most common childhood cancer, accounting for around one-third of all cancers in children. The second most common group of childhood cancers is malignancies of the central nervous system, including brain tumors. By comparison, lymphomas comprise only 10 percent of childhood cancers.
In contrast, many lymphomas are more common in people over the age of 55.
There is overlap, for example, as some chronic leukemias are much more common in older people, whereas Hodgkin’s lymphoma has its first peak in incidence between the ages of 15 and 40.
Both leukemias and lymphomas are considered “blood-related” cancers and involve cells that play an important in immune function. There are general differences between the two outlined above, yet when broken down by specific leukemias and lymphomas there is much overlap.
Perhaps a greater difference is to distinguish these blood-related cancers and “solid tumors.” In general, treatments which increase life expectancy have progressed further for those with advanced leukemias and lymphomas than for those with advanced solid tumors. For example, the discovery of the targeted therapy Gleevec (imatinib) has changed chronic myeloid leukemia from being an almost universally fatal disease to a condition we can now often treat as a chronic disease, controlling the disease for an indefinite period of time. Acute lymphocytic leukemia was at one time usually rapidly fatal, yet around 90 percent of children with this disease can now be cured. For those with Hodgkin’s lymphoma, the life expectancy has improved dramatically as well. This disease, which had a 10 percent 5-year survival rate a century ago, now has a 5-year survival rate of over 90 percent for early stage and well over 50 percent for stage 4 disease.
In contrast, many stage 4 solid tumors, such as breast cancer, lung cancer, and pancreatic cancer are not curable and are almost always fatal over time. That said, some approaches to treatment, such as targeted therapies and immunotherapy offer hope that those with solid tumors will eventually follow the advances in survival that many people with blood-related cancers now realize.
- American Cancer Society. Cancer Facts and Figures 2017.
- National Cancer Institute. Adult Hodgkin Lymphoma Treatment (PDQ) – Health Professional Version.
- National Cancer Institute. Adult Non-Hodgkin Lymphoma Treatment (PDQ) – Health Professional Version.
- National Cancer Institute. Childhood Acute Lymphoblastic Leukemia Treatment (PDQ) – Health Professional Version.