What Happens if a Mast Cell Tumor Goes Untreated?

If a mast cell tumor goes untreated, it can lead to a range of severe and potentially life-threatening health complications, both localized and systemic, significantly impacting an animal's quality of life and ultimately shortening their lifespan.

The Progressive Nature of Untreated Tumors

Mast cell tumors are a type of cancer that can vary greatly in their aggressiveness, from relatively benign to highly malignant. Without intervention, these tumors will continue to grow, potentially infiltrating surrounding tissues and causing significant local damage.

• Local Growth and Ulceration: As the tumor expands, it can become irritated, inflamed, and even ulcerate (open sores) on the skin's surface. This can lead to pain, itching, infection, and chronic bleeding at the tumor site. The affected area may appear red and swollen.
• Invasion of Surrounding Tissues: More aggressive tumors can extend deep into underlying muscle, fascia, or even bone, making them more difficult to manage and causing greater discomfort.

Dangerous Systemic Complications

One of the most concerning aspects of untreated mast cell tumors is their ability to cause systemic problems throughout the body due to a process called degranulation. Mast cells contain granules filled with powerful substances like histamine, heparin, and proteolytic enzymes. When the tumor is disturbed or spontaneously degranulates, these substances are released into the bloodstream, leading to a cascade of effects.

According to veterinary oncology insights, the release of these granule contents can cause a variety of serious issues:

• Gastrointestinal Distress: The release of histamine can stimulate gastric acid production, potentially leading to stomach ulceration and bleeding. This can manifest as vomiting, loss of appetite, black tarry stools (melena), or abdominal pain.
• Localized Swelling and Redness: While the tumor itself might be swollen and red, degranulation can also cause more widespread swelling and redness at and around the tumor site, indicating a significant inflammatory response.
• Life-Threatening Systemic Shock: In severe cases, the massive release of histamine can cause a dangerous drop in blood pressure, leading to anaphylactic shock or other profound systemic reactions that can be rapidly fatal if not addressed immediately.
• Coagulation Issues: The release of heparin can interfere with blood clotting, potentially leading to increased bleeding tendencies.

Metastasis and Worsening Prognosis

Perhaps the most dire consequence of an untreated mast cell tumor is its potential to metastasize, or spread, to other parts of the body. Once the cancer has spread, the disease becomes significantly more challenging to treat, and the prognosis worsens considerably.

• Common Metastatic Sites: Mast cell tumors frequently spread to regional lymph nodes, the spleen, liver, and bone marrow.
• Organ Dysfunction: As the cancer spreads to vital organs, it can impair their function, leading to organ failure and general decline in health.
• Reduced Survival Time: Without treatment, especially for higher-grade or metastatic tumors, the time an animal has left is often very limited, marked by increasing discomfort and illness.

Summary of Consequences

The table below outlines the primary consequences of an untreated mast cell tumor:

Given these severe potential outcomes, prompt veterinary evaluation and treatment are always recommended for any suspected mast cell tumor.