High Eosinophils and Certain Types of Cancer

High levels of eosinophils, also known as eosinophilia, may be a sign of certain types of cancers as well as other conditions like parasitic diseases, allergic reactions, autoimmune disorders, and fungal infections.

These white blood cells are part of the body's frontline immune defense and will increase in number in response to anything that the body considers harmful. Eosinophilia is a common feature of certain blood cancers, such as eosinophilic leukemia and Hodgkin lymphoma, as well as solid tumor cancers of the colon, lungs, breast, and others.

This article describes the function of eosinophils and the conditions associated with eosinophilia. It also explains how eosinophils are linked to cancer and what happens if you are diagnosed with eosinophilia.

The Function of Eosinophils

Eosinophils are a type of white blood cell that comprises 2% to 3% of the total white blood cells in your body. They are a part of your innate immune system, meaning the frontline defensive cells that attack anything the body considers harmful. (This differs from the acquired immune system in which cells are "programmed" to attack specific invaders.)

Eosinophils are responsible for combatting parasites and certain infections. They are also involved in allergic and autoimmune conditions in which the body reacts to harmless substances it mistakenly thinks are harmful.

Eosinophils are produced by the bone marrow and freely circulate in the bloodstream. But, they also reside in tissues, such as the colon, lungs, breasts, uterus, spleen, and lymph nodes.

Cause of Elevated Eosinophils

"Eosinophilia" is the term used to describe an abnormally high eosinophil count. Lab values can vary, but an eosinophil count of less than 500 cells per microliter of blood (cells/mL) is generally considered normal.

Anything over this may be described as follows:

• Mild eosinophilia: 500 to 1,500 cells/mL
• Moderate eosinophilia: 1.500 to 5,000 cells/mL
• Severe eosinophilia: Over 5,000 cells/mL

Eosinophilia can occur for many reasons. It can happen when the bone marrow is malfunctioning and produces too many eosinophils (referred to as primary eosinophilia). It can also occur when the immune system is activated in response to a disease outside of bone marrow (referred to as secondary eosinophilia).

Some of the major causes of eosinophilia can be broadly characterized as:

• Parasitic infections such as trichinosis and malaria
• Fungal infections such as coccidioidomycosis and aspergillosis
• Allergic conditions including asthma and drug allergies
• Skin disorders such as eczema and urticaria (hives)
• Autoimmune diseases such as inflammatory bowel disease (IBD)
• Endocrine disorders such as adrenal insufficiency

In addition, eosinophilia can develop in response to certain types of cancers.

Types of Cancer That Cause High Eosinophils

Cancers that cause eosinophilia may either be primary (involving the bone or bone marrow) or secondary (stemming from disease in other parts of the body).

Leukemia

Leukemia is a form of blood cancer that affects different types of blood cells, such as lymphoid cells (a type of white blood cell) or myeloid cells (a type of bone marrow cell).

The four most common types are acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), acute myeloid leukemia (AML), and chronic myeloid leukemia (CML).

Raised eosinophils are a feature of many types of leukemia, but the two forms characterized by hypereosinophilia include:

• Acute eosinophilic leukemia (AEL), a rare subtype of AML
• Chronic eosinophilic leukemia (CEL), a rare type of myeloproliferative neoplasm (a group of diseases in which the bone marrow makes too many blood cells)

Lymphoma

Lymphoma is a form of cancer affecting the lymphatic system (a group of organs that protects the body from infection and maintains a healthy balance of fluids in the body).

There are two main types:

• Non-Hodgkin lymphoma (NHL), the more common type that causes cancer in a type of white blood cells known as a lymphocyte
• Hodgkin lymphoma (HL), the least common type that can originate in any part of the lymphatic system
  

Eosinophilia can occur with both types of lymphoma, but hypereosinophilia is more strongly associated with HL.

Colorectal Cancer

Eosinophils are found in high concentrations in tissues of the gastrointestinal tract, including the colon and rectum. They, in fact, account for as much as 25% of the total white blood cell count in these tissues, the highest of any tissue in the human body.

Moreover, their numbers remain relatively steady over a lifetime, unlike eosinophils in other organs of the body.

In the presence of a solid tumor cancer, eosinophils will infiltrate the tumor itself, triggering the release of eosinophils from tissues into the bloodstream. Because the concentration of eosinophils in intestinal tissues is already high, the increase in numbers may be significant.

As such, eosinophilia may be an indication of colorectal cancer, especially if accompanied by other symptoms of the disease.

It has also been suggested that high eosinophils in a colon biopsy (obtained during colonoscopy) may be an early warning sign of colorectal cancer even if no actual cancer cells are found.

Lung Cancer

Eosinophils reside in other tissues of the body, albeit at a far lesser concentration. These include the lungs, thymus gland, uterus, and mammary glands. Unlike the gastrointestinal tract, however, eosinophil numbers in these tissues can fluctuate due to factors like hormones or age.

Because of these and other factors, an increase in eosinophils may not be as significant or a distinct "red flag" that cancer is involved.

Where eosinophils may have value in predicting the progression of certain cancers, most specifically lung cancer.

Research published in Frontiers of Medicine suggested that the development of eosinophilia in people with certain lung cancers was a risk factor for progression. This was especially true with squamous cell carcinoma, the type affecting the central airways of the lungs.

Next Steps

On their own, elevated eosinophils are not diagnostic of cancer. Furthermore, there is no distinct eosinophil level that indicates cancer. On its own, eosinophilia can occur for many reasons and cancer is only one of them.

With that said, high eosinophils may be suggestive of cancer if a person has symptoms of eosinophilic organ damage (also known as hypereosinophilic syndrome) and there is no evidence of a parasitic infection.

Symptoms of hypereosinophilic syndrome include:

• Urticaria (hives) or angioedema (a condition similar to hives involving deeper tissues)
• Dizziness
• Memory loss or confusion
• Cough
• Dyspnea (shortness of breath)
• Fatigue
• Fever
• Mouth sores

In such cases, your healthcare provider will order tests to rule out other possible causes of hypereosinophilic syndrome. If no cause can be found—or you have symptoms of cancer—other tests will be ordered to determine whether cancer is involved.

The tests and procedures may include:

• Bone marrow aspiration: The extraction of a sample of fluid from bone marrow using a thin needle
• Bone marrow biopsy: The removal of a sample of tissue from bone marrow using a larger, hollow core needle
• Chest computed tomography (CT): An imaging technique utilizing multiple X-ray images to detect abnormalities in the lungs, such as tumors
• Colonoscopy: A minimally invasive examination of the colon using a flexible fiber-optic scope that is inserted through the rectum
• Molecular testing: A lab evaluation of bone marrow or blood that can identify genes, proteins, and other factors unique to leukemia, lymphoma, and other types of cancers
  

Based on the initial findings, additional tests may be ordered to confirm that cancer is present and, if so, what type of cancer is involved.

Summary

Eosinophils are a type of white blood cell. High levels of eosinophils, or eosinophilia, can indicate many things, including parasitic diseases, fungal infections, autoimmune disorders, and allergies.

It can also be a sign of cancer. This includes blood cancers like leukemia and lymphoma, and solid tumor cancers like colorectal cancer and lung cancer. Although eosinophilia is not a sign of cancer, it may be suggestive of cancer if other causes have been eliminated.