Lymphoma is a type of blood cancer that originates in the lymphatic system. The lymphatic system is part of the immune system and is made up of a network of lymph nodes connected by lymph vessels. Lymph nodes are found throughout the body and act as filters for lymph fluid as it circulates. Lymphoma develops when lymphocytes, a type of white blood cell located within lymph nodes, undergo abnormal and uncontrolled cell division. As lymphoma cells multiply, they form tumors in the lymph nodes and other lymphatic tissues. Lymphoma has the potential to spread to almost any part of the body, but there are certain sites that are more commonly affected.
Lymph Nodes
The lymph nodes are the most common site of lymphoma involvement. Lymph nodes are located in clusters throughout the body along the pathways of the lymphatic system. There are hundreds of lymph nodes in the body, with the largest clusters found in the neck, underarms, chest, abdomen, and groin. Lymphoma often first develops in one or more lymph node regions before potentially spreading to others. The specific lymph nodes affected can vary based on the subtype of lymphoma. Some of the most frequently involved lymph node sites include:
- Cervical lymph nodes – located in the neck
- Axillary lymph nodes – located under the arms
- Mediastinal lymph nodes – located in the chest between the lungs
- Mesenteric and retroperitoneal lymph nodes – located in the abdomen and pelvis
- Inguinal lymph nodes – located in the groin area
When lymphoma cells multiply in the lymph nodes, it causes the nodes to abnormally enlarge, which is often one of the first signs of the disease. Lymph nodes affected by lymphoma are usually painless in the early stages. As the disease advances, they may become painful and swollen.
Spleen
The spleen is another lymphatic organ that is frequently involved in lymphoma. The spleen functions to filter blood as part of the immune system. It contains white pulp that is comprised of lymphocytes and also acts as a reservoir for blood. In lymphoma, cancerous lymphocytes accumulate in the spleen causing it to enlarge. Splenic enlargement, known as splenomegaly, occurs in roughly 1 out of 3 lymphoma cases. The degree of enlargement depends on the extent of lymphoma spread within the spleen. Massive splenomegaly can cause abdominal discomfort or pain. Rupture of the enlarged spleen is a potential complication.
Bone Marrow
The bone marrow produces blood cells, including lymphocytes. The marrow cavities within bones provide an environment for hematopoiesis – the generation of blood cells. In lymphoma, cancerous lymphocytes can invade the bone marrow. This is referred to as marrow involvement or marrow infiltration. Diffuse marrow involvement occurs in roughly 1 out of 5 lymphoma patients. Lymphoma cells displace normal hematopoietic cells in the marrow, leading to abnormal blood counts. Anemia and low platelet counts are common complications.
The Gastrointestinal Tract
The GI tract is a site for extranodal lymphoma, meaning lymphoma originating outside the lymph nodes. This occurs more often with non-Hodgkin lymphoma than Hodgkin lymphoma. Diffuse large B-cell lymphoma and mantle cell lymphoma are aggressive NHL subtypes that frequently involve the GI tract. The most common sites are:
- Stomach
- Small intestine
- Colon
- Rectum
Lymphoma infiltration can lead to thickening of the intestinal wall, obstruction, abdominal pain, and GI bleeding.
Chest
Lymphoma can spread to sites within the chest cavity:
- Lungs – Lymphoma may directly invade the lungs or spread there through the bloodstream. Lung nodules or masses can develop. This can cause cough, shortness of breath, chest pain.
- Pleura – The pleura are membranes surrounding the lungs. Lymphoma can spread along the pleura causing pleural effusions – fluid buildup between the pleural layers.
- Pericardium – The pericardium is the membrane around the heart. Similar to the pleura, lymphoma may spread along the pericardium leading to pericardial effusion – fluid accumulation.
Skin
Primary cutaneous lymphomas arise initially in the skin. But lymphoma can secondarily involve the skin through spread from lymph nodes or internal organs. Skin manifestations vary widely, ranging from isolated lesions to diffuse skin involvement. Some skin findings in lymphoma include:
- Red or purple patches or plaques
- Nodules or tumors
- Itchy rashes
Brain and Spinal Cord
The brain and spinal cord make up the central nervous system (CNS). CNS lymphoma refers to lymphoma arising within or spreading to the brain, spinal cord, meninges (membranes covering the CNS), or eyes. CNS involvement occurs in roughly 5% of NHL cases but is rare with Hodgkin lymphoma. It may develop as a mass lesion within the brain or as leptomeningeal disease – diffuse seeding along the meninges. Symptoms depend on the location but may include headache, altered mental status, vision changes, or neurologic deficits.
Other Sites
While less common than the organs already described, lymphoma can potentially spread to almost any body site. Additional sites may include:
- Liver – Can cause hepatomegaly (enlarged liver) and liver dysfunction.
- Kidneys – Can obstruct flow of urine and cause kidney failure.
- Adrenal glands – Can lead to adrenal insufficiency.
- Bone – Lymphoma cells can form bone tumors causing pain or fractures.
- Soft tissues – Can involve muscles, body cavities, connective tissues.
Distribution Patterns
There are certain patterns in how lymphoma tends to spread:
- Nodal – Primarily involves lymph nodes, often starting in one region then spreading to others.
- Extranodal – Originates in organs or tissues outside lymph nodes.
- Mixed – Involves both nodal and extranodal sites.
Over half of NHL cases have exclusively nodal involvement at diagnosis. But extranodal NHL makes up around 40% of cases. Hodgkin lymphoma more typically follows a nodal pattern. Bone marrow, spleen, and liver are the most common sites of extranodal involvement. The distribution pattern impacts prognosis and is used for lymphoma staging.
Most Commonly Affected Sites By Lymphoma Subtype
| Lymphoma Subtype | Most Commonly Affected Sites |
|---|---|
| Diffuse Large B-Cell Lymphoma | Lymph nodes, GI tract, bone marrow, Waldeyer ring |
| Follicular Lymphoma | Lymph nodes, bone marrow, spleen |
| Mantle Cell Lymphoma | Lymph nodes, bone marrow, GI tract, spleen |
| Marginal Zone Lymphomas | Lymph nodes, bone marrow, spleen, stomach |
| Burkitt Lymphoma | Lymph nodes, bone marrow, central nervous system, kidneys, ovaries |
| Hodgkin Lymphoma | Lymph nodes, spleen, liver, bone marrow |
Conclusion
In summary, while lymphoma can potentially involve any body site, certain areas are more commonly affected due to the anatomy of the lymphatic system. Regional lymph nodes and lymphatic organs like the spleen are most often impacted first. As the disease advances, lymphoma may metastasize to other lymph nodes or extranodal sites via lymphatic channels or the bloodstream. The specific pattern of spread is influenced by the particular lymphoma subtype. Understanding the typical sites of involvement for each type allows for tailored staging, prognostication, and treatment approaches that target the regions most likely to be affected. Monitoring these sites is key during treatment and follow up to assess response.