The Role Eosinophils Play in Cancer

Eosinophils are a type of white blood cell produced in the bone marrow that makes up about 5 percent of the total number of white blood cells. Eosinophils can circulate in the blood and also are found outside blood vessels in other organs in the body. The gastrointestinal (GI) tract typically has the highest number of eosinophils relative to other organs.

Woman with cancer reviews test results with doctor
FatCamera / Getty Images

The Function of Eosinophils

Eosinophils protect the body by killing bacteria and parasites, but can cause problems when they react incorrectly and cause allergies and other inflammatory reactions in the body. For example, food allergies can cause too many eosinophils to gather in the digestive tract, which may lead to symptoms such as diarrhea and damage to the cells lining the GI tract.

Eosinophils are part of the innate immune system, which means that they can "non-specifically" destroy any invaders they encounter in the body, such as bacteria and parasites. Eosinophils do not have to recognize the invader specifically, but instead simply recognize the invader as something that is foreign to the body and should not be present.

When There Are Too Many Eosinophils

When a large number of eosinophils are dispatched to a certain site in the body, or when the bone marrow produces too many eosinophils, a condition known as eosinophilia exists. Eosinophilia can result from a variety of conditions, diseases, and factors, including:

In addition, eosinophilia can develop in response to certain cancers, including:

Eosinophils and Colorectal Cancer

The number of eosinophils in the blood can rise during a normal response to allergic reactions, fungal and parasitic infections, medications, and some types of cancer.

A study published in the journal Modern Pathology in 2014 looked at how eosinophils might predict outcomes for patients with colorectal cancer. Although staging of colorectal cancer typically is based on information about the tumor itself, lymph node involvement, and the presence of metastases (cancer spread to other sites), often two patients with the same staging will have dramatically different outcomes.

The study's authors examined whether eosinophil levels in or around a colorectal tumor helped predict outcome. They concluded that higher numbers of eosinophils around the primary colorectal tumor were associated with an improved patient outcome and, as a result, that eosinophils should be routinely counted during tumor examination.

Was this page helpful?
9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Blumenreich MS. The White Blood Cell and Differential Count. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 153. Available from:

  2. Mehta P, Furuta GT. Eosinophils in Gastrointestinal Disorders: Eosinophilic Gastrointestinal Diseases, Celiac Disease, Inflammatory Bowel Diseases, and Parasitic InfectionsImmunol Allergy Clin North Am. 2015;35(3):413–437. doi:10.1016/j.iac.2015.04.003

  3. Ramirez GA, Yacoub MR, Ripa M, et al. Eosinophils from Physiology to Disease: A Comprehensive ReviewBiomed Res Int. 2018;2018:9095275. Published 2018 Jan 28. doi:10.1155/2018/9095275

  4. Shamri R, Xenakis JJ, Spencer LA. Eosinophils in innate immunity: an evolving story. Cell Tissue Res. 2011;343(1):57–83. doi:10.1007/s00441-010-1049-6

  5. Kovalszki A, Weller PF. EosinophiliaPrim Care. 2016;43(4):607–617. doi:10.1016/j.pop.2016.07.010

  6. Long H, Zhang G, Wang L, Lu Q. Eosinophilic Skin Diseases: A Comprehensive ReviewClin Rev Allergy Immunol. 2016;50(2):189–213. doi:10.1007/s12016-015-8485-8

  7. Beishuizen A, Vermes I, Hylkema BS, Haanen C. Relative eosinophilia and functional adrenal insufficiency in critically ill patientsLancet. 1999;353(9165):1675–1676. doi:10.1016/s0140-6736(99)01346-x

  8. Prizment AE, Vierkant RA, Smyrk TC, et al. Tumor eosinophil infiltration and improved survival of colorectal cancer patients: Iowa Women's Health StudyMod Pathol. 2016;29(5):516–527. doi:10.1038/modpathol.2016.42

  9. Harbaum L, Pollheimer MJ, Kornprat P, Lindtner RA, Bokemeyer C, Langner C. Peritumoral eosinophils predict recurrence in colorectal cancer. Mod Pathol. 2015;28(3):403-13.

Additional Reading
  • Modern Pathology. "Peritumoral eosinophils predict recurrence in colorectal cancer."

  • Journal of Clinical Oncology. 29:2011. "Peripheral blood eosinophil counts and risk of colorectal cancer mortality in a large general population-based cohort study."