Leukocytosis refers to an elevated white blood cell (WBC) count in the blood. While a high WBC count can sometimes be a symptom of cancer, it is far more commonly linked to other, less severe conditions. Understanding the various reasons behind an increased white blood cell count can help clarify this common laboratory finding.
Understanding Leukocytosis
White blood cells, or leukocytes, are a vital part of the immune system, protecting against infection and disease. Produced in the bone marrow, they identify and combat foreign invaders. There are five primary types: neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
Leukocytosis is diagnosed when the total white blood cell count exceeds the normal range, typically 4,000 to 11,000 cells per microliter for healthy adults. An elevated count indicates the body is responding to a stimulus, often infection or inflammation, by increasing white blood cell production. Leukocytosis is a laboratory finding, not a disease.
Common Non-Cancerous Causes
An elevated white blood cell count is most frequently a normal physiological response. Infections are a leading cause, as the body increases white blood cell production to fight off invaders like bacteria or viruses. Conditions like pneumonia or appendicitis often cause a temporary increase.
Inflammation, from autoimmune disorders, inflammatory bowel disease, or tissue damage, can also trigger leukocytosis. The immune system signals the bone marrow to produce more white blood cells for healing. Physical and emotional stress, including exercise, surgery, or acute illness, can transiently elevate white blood cell counts due to stress hormone release.
Certain medications, such as corticosteroids, lithium, and beta-agonists, can cause leukocytosis by influencing white blood cell production. Other non-cancerous factors include smoking, pregnancy, obesity, common allergies, or spleen removal, all of which can lead to persistently higher white blood cell counts.
Leukocytosis and Cancer
While less common, leukocytosis can be associated with certain cancers, particularly those affecting the blood and bone marrow. Leukemias, for instance, are cancers where the bone marrow produces an excessive number of abnormal, non-functional white blood cells. Both acute and chronic leukemias can lead to a significantly elevated white blood cell count due to this uncontrolled proliferation.
Lymphomas, cancers originating in the lymphatic system, can also increase white blood cell count due to abnormal lymphocyte growth. Beyond blood cancers, solid tumors in organs like the lung, kidney, or colon can cause leukocytosis. This often occurs through paraneoplastic syndromes, where tumor cells stimulate the bone marrow to produce more white blood cells.
The specific type of white blood cell elevated can provide clues to the underlying cause, including cancer. For example, increased neutrophils (neutrophilia) are common in infections and some solid tumors, while increased lymphocytes (lymphocytosis) might suggest viral infections or certain leukemias. An extreme elevation, exceeding 100,000 cells per microliter, often warrants immediate evaluation for conditions like leukemia.
When to Seek Medical Advice
Leukocytosis is frequently discovered incidentally during routine blood tests, such as a complete blood count (CBC). If identified, a healthcare provider will review your medical history and conduct a physical examination to look for accompanying symptoms or signs of an underlying condition.
Seek medical attention if leukocytosis is accompanied by symptoms such as persistent fever, unexplained weight loss, night sweats, unusual fatigue, or swollen lymph nodes. Other concerning signs include recurrent infections, easy bruising, or abnormal bleeding. Further diagnostic steps may include additional blood tests, a peripheral blood smear, or a bone marrow biopsy if a disorder is suspected. Only a medical professional can accurately determine the cause and recommend the appropriate course of action.