Non-Hodkins Lymphoma – Tissue and Systems

This article describes the basic anatomy and function of the lymphatic system in order to better understand the disease class of Non-Hodgkin’s Lymphoma.  The term lymphoma is about as broad and generic as the term cancer.  The word “lymph” is derived from a latin root meaning water.  The suffix “–oma” refers to a swelling or tumor of the prefix.  A thumbnail sketch of the immune system will be described.  Non-Hodgkin’s Lymphoma simply refers to any lymphoma that is not Hodgkin’s Lymphoma, thus it describes many different kinds of lymphoma.  Knowledge of all these subtypes is not necessary as many have similar symptoms.  The important point from a public health perspective is to be aware of the “red flag” symptoms and to bring these to the attention of your doctor for further investigation.

As blood circulates throughout the body, there is a small leak of water through the vessels and around cells of the body.  This extracellular water is collected by specialized vessels and sent back to the blood stream.  This space outside of blood vessels and in-between cells is where a major part of the immune system occurs.  The immune system is a collection of defense mechanisms that fights off foreign invaders such as bacteria, viruses and help control rouge cells that may become cancer.  If the lymph system was clogged or dysfunctional, the area upstream from this site would swell massively due to accumulation of this extra-cellular fluid.  A classic example of this is with infection of the parasite W. bancrofti (also known as filariasis).  The lymphatic fluid is collected into transport vessels that go through a series of processing and collection points known as lymph nodes.  There are organized groups of lymph nodes in several key regions of the body such as the abdomen, armpit and groin.

Lymph nodes are processing centers of the immune system that screen lymph fluid for hostile invaders such as bacteria and try to remove them.  Preventing them from spreading throughout the body prevents bacteremia and sepsis. The lymph nodes are more than a simple filter, they have collections of lymphocyte cells such as T-cells and B-Cells.

The cells of the immune system are very complex and are able to interact with each other through messaging to control different kinds of infections.  These cells have the ability to recognize “self” from “non-self” and help destroy foreign invaders or bodily cells that are infested with an abnormality such as a virus.  A partial list of cells involved in the immune system includes:

  • T-cell lymphocytes – white blood cells that have broad control over immune system and occur in several types, during development they are “trained” to recognize self and non-self (a process known as positive and negative selection)
  • B-cell lymphocytes – white blood cells that assist T-cells in remembering pathogens, producing antibodies and helping clear infected cells.
  • Natural Killer (T) Cells – white blood cells that can independently induce cell death if infected
  • Plasma (B) Cells – B-cells that live in lymph nodes and secrete antibodies.
  • Memory Cells – white blood cell (t-subtype) that can rapidly respond to a “remembered” foe
  • T-Helper Cells –  white blood cells that recognize and organize other cells in specific defesne
  • T-Cytotoxic Cells – white blood cells that recognize infected cells and help destroy them
  • Neutrophils – white blood cells that can ingest or destroy bacteria directly
  • Eosinophils – white blood cells that help fight parasites
  • Basophils – white blood cells that help fight parasites and participate in allergy
  • Mast Cells – white blood cells that help immune function, allergy and healing
  • Dendritic Cells – white blood cell that lives in the skin and detects invaders
  • Macrophages – white blood cells that help identify and destroy invaders, organizers

This is actually a very simplified list of components and functions.  Organs and tissue involved in the lymphatic / immune system also include the lymphatic vessels, lymph nodes, thymus, and spleen.  The white blood cells are produced mostly in the bone marrow.  Antibodies are circulating markers or tags that can “stick” to a foreign invader and identify them for attack and removal.  There are many non-specific antibodies and some that can be made in mass amounts if an old foe is recognized.

Lymphoma is a cancer or abnormal growth of one or several parts of the lymphatic system.  Lymphoma is largely a tumor of the lymph nodes.  The granulocyte white blood cells made in the bone marrow can be overproduced and crowd the blood.  This is known as leukemia.  Both leukemia and lymphoma involve overproduction and excessive growth of some aspect of the immune system.

Diffuse large B-cell lymphoma is the most common type of non-Hodgkin’s lymphoma.  It makes up about 40% of all lymphomas in adults.  Up to 50% of people with this sub-type can be cured with chemotherapy.  This is encouraging but it still emphasizes the poorer prognosis compared with Hodgkin’s Lymphoma where up to 90% of people are cured with treatment.  Burkitt Lymphoma is another type of NHL.  There are several different types of Burkitt Lymphoma but in general these are more aggressive and have a poorer prognosis.  About 20% of NHL occurs as follicular lymphoma.  This type tends to have a better prognosis than other types of NHL.  A type of NHL that tends to occur mostly in elderly men > 65 years old is mantle cell lymphoma.  This sub-type is also aggressive and usually has a poor prognosis.

There are many different types of lymphoma but they generally fall under two categories, Hodgkin’s and non-Hodgkin’s types.  Tumors of the lymph nodes will impair their function.  The two major functions of the lymphatic system and lymph nodes are to help return extra-cellular water back to the blood and to process potential invaders to assist with immunity and protection of the body from infection.  If the lymph nodes are unable to carry out these functions because of damage, removal, parasitic infection (such as the above example with filariasis), or tumor – then both swelling and infection will occur more frequently.

Tumors of lymph nodes are generally noticeable as they usually occur in areas that are easily seen or felt.  It is not uncommon to have “swollen glands” with mild infection such as sore throat.  There are large amounts of lymph nodes collected in regions such as the neck, armpit and groin.  With infection these lymph nodes enlarge to help process more fluid and bacteria from that area.  This is normal healthy response and does not represent disease.  When these lymph nodes become very large, non-tender, and rubbery feeling then this is an abnormal appearance and usually prompts some type of investigation.  The most information is obtained by getting a sample of the cells in the swollen lymph nodes to see what they look like under a microscope.  These cells can undergo further testing to help classify the type of cancer as well.  This sampling process is also known as lymph node biopsy.

REFERENCES:

  1. www.cancer.gov/cancertopics/types/hodgkin
  2. www.nlm.nih.gov/medlineplus/lymphoma.html
  3. Lichtman MA. Obesity and the risk for a hematological malignancy: leukemia, lymphoma, or myeloma. Oncologist 2010; 15:1083.
  4. Abeloff, M.D. (2008). Abeloff: Abeloff’sClinical  Oncology, 4th ed. Chapter 112. Philadelphia, PA: Churchill Livingstone – Elsevier
  5. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.