Many people assume that a major disease like skin cancer will cause a change in their complete blood count (CBC). Skin cancer is the most frequently diagnosed cancer globally, including types like basal cell carcinoma, squamous cell carcinoma, and melanoma. White blood cells (WBCs), or leukocytes, are the body’s primary defense cells, and a blood test measures their total number circulating in the bloodstream. The expectation is that cancer, as a significant health threat, would prompt a noticeable immune system response.
The Role of White Blood Cells in Immune Response
White blood cells are the mobile components of the immune system that constantly patrol the body to identify and neutralize threats. Their primary function is to respond to foreign invaders, tissue damage, or severe inflammation. These cells are categorized into several types, including neutrophils, lymphocytes, and monocytes. An elevated total WBC count, known as leukocytosis, signals that the body is mounting a systemic defense. This elevation occurs when the bone marrow rapidly produces and releases new cells in response to chemical signals called cytokines.
Localized Skin Cancer and the Systemic WBC Count
In the most common scenarios, early-stage or localized non-melanoma skin cancers like Basal Cell Carcinoma (BCC) and Squamous Cell Carcinoma (SCC) are unlikely to cause a measurable elevation in the systemic white blood cell count. These cancers are often slow-growing and contained within the skin layers. The immune response they provoke is primarily localized at the tumor site, not a massive, body-wide systemic reaction. Studies have shown that overall WBC counts may even be lower in patients with localized BCC and SCC compared to healthy individuals. Therefore, a normal WBC count on a standard blood panel should never be used to rule out the presence of skin cancer.
Factors That Cause WBC Count Changes in Cancer Patients
While early, localized skin cancer rarely affects the WBC count, significant changes can occur in more advanced situations. The most common reason for leukocytosis is a secondary infection, especially if the tumor has ulcerated or broken the skin barrier. An open wound can lead to a localized infection like cellulitis, which triggers a robust systemic immune response and causes a spike in circulating neutrophils.
More advanced stages of cancer, such as metastatic melanoma, can directly influence blood cell production. If the cancer spreads to the bone marrow, it disrupts normal blood cell production, potentially causing an abnormally high or low count. Advanced cancers can also generate a massive inflammatory state, leading to sustained leukocytosis that indicates a poor prognosis.
A specific, though rare, cause of a raised WBC count is a paraneoplastic syndrome. In these cases, the tumor, often metastatic melanoma, secretes hormone-like substances such as granulocyte colony-stimulating factor (G-CSF). This ectopic production directly stimulates the bone marrow to overproduce neutrophils, resulting in paraneoplastic granulocytosis.
Conversely, many skin cancer patients undergoing treatment will experience a drop in their white blood cell count. Chemotherapy and radiation therapy kill rapidly dividing cells, including healthy blood-producing cells in the bone marrow. This often leads to neutropenia, an abnormally low neutrophil count, making the patient highly susceptible to serious infection. Patients may be given synthetic G-CSF to counteract this effect, which can temporarily cause the WBC count to rise.
How Skin Cancer is Actually Diagnosed
Since a routine blood test is not a reliable screening tool, skin cancer diagnosis relies on visual and pathological examination. The first step involves a visual inspection of suspicious lesions, often guided by the ABCDE rule. This mnemonic identifies warning signs: Asymmetry, irregular Border, varied Color, Diameter, and Evolving appearance. If a suspicious lesion is identified, a dermatologist may use a dermatoscope to examine the lesion’s subsurface structures. The definitive diagnostic procedure is a biopsy, where a tissue sample is removed and sent to a lab for microscopic analysis. Blood work is utilized later, if at all, for assessing overall health, monitoring treatment side effects, or checking for signs of advanced disease.