Lymphoma Definition and Introduction

Doctor going over results of tests with patient.

Overview

Like other cancers, lymphoma involves abnormal growth of cells – the lymphoma cells grow and multiply or fail to die on time. In other words, they grow unchecked. As the lymphoma cancer grows, it can begin to affect the normal functions of the body as other tissues and organs become involved with the malignancy.

What Is the Lymph System?

The lymph system is an interconnected network of thin tubes and nodes that filter and circulate a fluid called lymph.

This analogy is oversimplified, but the lymph system can be thought of as a highway system, with lymph nodes and other organs serving as the rest stops. Lymphocytes – the white blood cells involved in lymphoma – naturally move about the body. In other words, healthy lymphocytes already have the ability to move to other structures and sites in the body. So, when a lymphoma starts in the lymph nodes and spreads to other places, it is called migration or extranodal involvement rather than metastasis; this is in contrast to breast cancer or prostate cancer, for instance, in which involvement at distant sites is considered metastasis, or metastatic disease.

Lymph nodes are packed with white blood cells, which help fight infections and are vitally important to our well being. The lymph system is an important part of the immune system, which is comprised of many different cell types. The type of white blood cell that becomes cancerous in lymphoma is the lymphocyte.

There are different types of lymphocytes, and cancer may develop in each type. For this reason, there are all different types of lymphoma, including B-lymphocyte lymphomas, T-lymphocyte lymphomas, and many different subtypes of each. In lymphoma, cancerous lymphocytes may grow abnormally beginning in the lymph nodes – or, the malignancy may start elsewhere in the body.

Which Part the Body Is Affected?

Lymphoma may affect any of the parts of the lymph system. Most commonly, patients first notice an enlargement of lymph nodes – usually in the neck, groin or armpits.

Outside the Lymph Nodes:

However, lymphomas can occur in other organs as well. This is because lymphoid tissue can be found almost anywhere in the body. Lymphoid tissue includes both cells and organs. Cells – including white blood cells, and organs – including the thymus, bone marrow, lymph nodes and spleen. Most lymphomas begin in the lymph nodes.

In addition to organs, special areas of lymphoid tissue include collections of cells located throughout the body, at strategic sites to fight off invaders. Examples of these sites include the tonsils, certain areas in respiratory tract, in lymphoid patches beneath moist mucous membranes – such as those of the gastrointestinal tract – and other tissues of the body.

One Disease, or Many?

Lymphoma is not a single cancer but a group of related cancers. In fact, when you include rare forms, there are scores and scores of lymphoma types.

Broadly, lymphomas are grouped under two categories: Hodgkin Disease versus non-Hodgkin Lymphoma. These two broad groups may be similar in their symptoms and the tests that are required, but they behave differently and have other important differences.

Non-Hodgkin’s lymphoma, which accounts for nearly 90 percent of all lymphomas, is comprised of far more types than Hodgkin's lymphoma.

Hodgkin’s lymphoma refers specifically to the kind of lymphoma first described by Thomas Hodgkin, a doctor who lived in the early 1800s. Hodgkin lymphoma has two peak age groups -- one in the 20s and one in the 80s.

How Is Lymphoma Different From Leukemia?

Leukemia and lymphoma have much in common -- they are both cancers involving white blood cells, and both can have implications for immunity and the risk of infection.

The two diseases are defined differently, however, and one key difference is that leukemia tends to begin in the blood-forming cells of the bone marrow and may be associated with high levels of white blood cells in the bloodstream, while most lymphomas begin in the lymph nodes and other lymphoid tissues.

Other key differences are listed in the article, 5 Major Differences Between Leukemia and Lymphoma.

Causes

In most lymphomas, there is no clear-cut cause, per se. That is, many lymphomas are believed to develop due to a combination of genetic and, potentially, environmental factors. The result is that scientists speak in terms of risk factors.

Risk factors are things that have been found to be associated with lymphoma but that won't necessarily or reliably cause lymphoma in all cases. Risk factors for different lymphomas can be distinct, and some are quite controversial, such as the weedkiller, Roundup.

Certain pesticides have been implicated in lymphoma risk, but in many cases there is no 'smoking gun.' Certain bacteria, viruses and even parasites can increase the risk for lymphoma. However, often there are other important individual factors in play, including genes and individual differences in the body's immune response to these infections. Certain treatments that suppress the immune system may also raise lymphoma risk.

In some cases, inherited genetic changes, or those present at birth, are believed to greatly influence the development of malignancy. In other cases, genetic changes in healthy white blood cells are to blame. When bits of chromosomes become rearranged or when bits go missing, this can lead to a predisposition for lymphoma; and in some cases, particular genetic changes in the lymphoma cells are associated with a better or worse prognosis.

Treatment

Treatments are best considered in view of the particular type of lymphoma. Chemotherapy, radiation, surgery and newer targeted therapies such as rituximab are all potentially relevant for various lymphomas. Often combined treatment, such as chemotherapy together with radiation, will be planned.

However, it really depends on which type of lymphoma it is, where in the body it is, and what the goals of treatment are for the individual patient. Some slow-growing lymphomas may be monitored at first rather than treated with chemotherapy.

A Word from Verywell

Getting up to speed on lymphoma can be a part time job, especially if you are recently diagnosed or entering a new phase of your journey. Educational and advocacy groups can be a big help, and here are just a few of the groups that can be found on the web:

The Leukemia & Lymphoma Society (LLS) is the world’s largest voluntary health agency dedicated to finding cures for leukemia, lymphoma, myeloma and other blood cancers. The LLS’s Team In Training, affectionately known as TNT, is arguably the most effective endurance charity program of its kind. From its start way back in 1988, TNT has grown to become the largest in its niche, with runners, walkers, triathletes, cyclists and hikers numbering over half a million…and counting. The American Cancer Society is a good source for basic information about the more common lymphomas. The Lymphoma Research Foundation is also a good resource. Lymphomation.org has plenty of information; in particular, Lymphoma Simplified - how it begins lays the groundwork for understanding how the different types of therapies work. Mobile apps have also made their entrance into the world of lymphoma advocacy, and new ones are likely to continue to be developed.

Sources:

American Cancer Society. Cancer Facts and Figures, 2017. Accessed July 2017.

American Cancer Society. Cancer in Children. Accessed July 2017.

The Leukemia and Lymphoma Society. Facts and Statistics. Accessed July 2017.

American Cancer Society. Leukemia--Chronic Lymphocytic. Accessed July 2017.

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