4.8/5 Stars (700+ Online Reviews)
TL;DR
Mast cell tumors (MCTs) are the second most common skin tumor in cats, often appearing as small lumps on the head, neck, or limbs. These cutaneous tumors are typically low-grade and slow-growing. Surgical removal is the treatment of choice, and many cats live a full, healthy life if the tumor is caught early and removed completely.
Visceral MCTs, especially splenic tumors, are more serious. A splenectomy (removal of the spleen) may extend life by 12–19 months if done before the cancer spreads. However, splenic MCTs and other internal forms are often detected later, harder to treat and often come with more severe clinical signs like vomiting, weight loss, or lethargy.
If the cancer has metastasized to other organs or bone marrow, survival may be limited to 1–4 months, though medications like steroids or chemotherapy may offer short-term relief. Once symptoms become unmanageable, the focus shifts to quality of life, palliative care, or compassionate euthanasia.
Life Expectancy Depending on Tumor Type and Stage
A cat’s life expectancy after being diagnosed with a mast cell tumor (MCT) depends on several key factors:
- the tumor’s location (cutaneous vs. visceral),
- its grade,
- and whether it has metastasized.
Some tumors can be completely removed with surgery, allowing cats to return to a normal routine. Others are more aggressive and may limit survival to just a few months.
Here’s what to expect depending on the type and progression:
- Cutaneous (Skin) Mast Cell Tumors: These tumors typically appear as small lumps on the skin—often around the head, neck, or limbs. Most are low-grade and can be successfully removed with surgery.
- When caught early and fully excised with clean margins, many cats live a full, healthy life. Recurrence is uncommon in low-grade tumors, though follow-up monitoring is still important to catch any changes early. This type has the most favorable long-term prognosis.
- Visceral (Internal) Mast Cell Tumors: These affect organs like the spleen or intestines. If the tumor is detected early and removed before it spreads, surgical treatment may offer 12 to 19 months of additional time. However, visceral MCTs are generally more aggressive than skin tumors and may cause serious systemic symptoms, even with treatment. The outcomes vary depending on the tumor’s location, grade, and the cat’s overall health.
- Metastatic Mast Cell Tumors: If the cancer has spread (metastasized) to the lymph nodes, bone marrow, or other organs, the prognosis is significantly more guarded. Most cats with advanced MCTs live only 1 to 4 months, depending on how well symptoms are managed and whether palliative care is pursued. In some cases, steroids or chemotherapy may offer brief relief, but the overall prognosis remains limited.
What Affects Your Cat’s Quality of Life
Beyond life expectancy, quality of life is one of the most important considerations after a mast cell tumor diagnosis. Several factors influence how your cat will feel on a daily basis and how well they tolerate treatment:
Tumor Location and Cell Type
Tumors on the skin, especially well-differentiated, low-grade ones, often behave more like benign growths. In contrast, internal tumors (like splenic or intestinal MCTs) tend to be more invasive and cause widespread illness, including gastrointestinal symptoms or organ dysfunction.
Early vs. Late Detection
Catching a tumor early (such as noticing a small lump during routine petting) can dramatically improve your cat’s outcome. Tumors found only after more severe symptoms emerge (like vomiting, weight loss, or lethargy) are often more advanced and harder to treat effectively.
Surgical Success
The ability to fully remove the tumor with clean surgical margins makes a big difference. When no cancer cells are left behind, the risk of recurrence drops significantly. Partial removal or high-grade tumors are more likely to return or spread.
Age and Overall Health
Younger, otherwise healthy cats typically recover from surgery and other treatments more easily. Older cats, or those with concurrent conditions like chronic kidney disease or diabetes, may face a more complicated recovery and reduced treatment options.
Symptom and Pain Management
Mast cell tumors can release histamine, leading to uncomfortable symptoms like itchiness, nausea, ulcers, or swelling. Managing these effects with medication, such as antihistamines, steroids, or anti-nausea drugs, can greatly improve your cat’s comfort, even if the tumor itself can’t be cured.
Recognizing When Treatment Is No Longer Enough
Even with early detection and aggressive treatment, some mast cell tumors will eventually reach a point where they can no longer be managed. In these cases, it becomes less about how much time is left and more about how your cat is feeling during that time.
You may start to notice signs that your cat is no longer responding well to medications, or that the side effects of treatment are outweighing the benefits. Quality of life, not survival time becomes the most important consideration.
Veterinarians often look at a combination of the following when helping you decide if it’s time to shift from active treatment to palliative or hospice care:
- Is your cat eating less, grooming less, or interacting less than normal?
- Are symptoms like vomiting, pain, or confusion getting worse?
- Is your cat hiding more, sleeping excessively, or showing signs of distress?
When the answer to several of these questions is “yes,” it may be time to focus on comfort, and begin preparing for end-of-life decisions.
Some symptoms may be managed with palliative or hospice support, while others may indicate that saying goodbye could be the kindest choice. Every cat is different, and so is every journey.
Here are some signs to watch for:
Ongoing vomiting or diarrhea that no longer improves with medication
→ These symptoms can often be managed for a time with medications, fluids, and dietary changes. But if they persist and begin causing distress or dehydration, it may be a sign that your cat’s body is no longer coping well.
Loss of appetite and noticeable weight loss
→ Some cats can be supported with appetite stimulants or assisted feeding if they’re still engaged and responsive. But if your cat consistently refuses food and seems withdrawn or tired, it may be time to re-evaluate their care plan, especially because when a cat isn’t eating and is losing weight, their body no longer has what it needs to regain strength. Without adequate nutrition, meaningful recovery becomes very unlikely.
Tumors that are bleeding, infected, or growing quickly
→ If the affected area can be kept clean and your cat is comfortable, hospice care may still be an option. However, frequent infections or signs of pain when resting or moving are indicators that comfort is becoming harder to maintain.
Changes in behavior, such as hiding or seeming disoriented
→ These can be signs of discomfort or cognitive decline. Some cats may still find reassurance in your presence and routine, while others may begin to withdraw more fully as they decline.
Difficulty breathing or open-mouth breathing
→ This is typically a sign that the cancer has spread to the lungs or chest cavity. This is an emergency condition and requires immediate intervention, whether this is hospitalization or euthanasia.
What It Means for You and Your Cat
When your cat is facing a progressive or terminal illness, the question often changes from how much time is left to how that time is spent. At this stage, your role becomes less about fixing and more about supportive care and simply being there: offering quiet comfort, paying attention to what brings them peace, and making decisions that honor their needs.
If you’re starting to see changes in your cat’s behavior or health, you’re not alone in wondering what comes next. This guide can help you understand the signs, weigh your options, and approach the decision with clarity and care:
When to Euthanize a Cat: Making the Hardest Decision
Choosing to say goodbye is never easy. But it can be peaceful, familiar, and filled with love.
At Compassionate Care, we offer in-home euthanasia throughout Portland and surrounding areas, so your cat can stay where they feel most at ease at home, with you.
FAQ
Are cutaneous mast cell tumors in cats considered cancer?
Yes. Cutaneous mast cell tumors (MCTs) are classified as a type of skin cancer. However, in cats, most of these tumors are low-grade and behave more like benign growths, meaning they grow slowly, rarely spread, and often don’t return after complete surgical removal. So while they are technically cancerous, their behavior is typically non-aggressive. Your veterinarian or DVM can confirm the tumor’s characteristics through a biopsy and advise on whether further treatment or monitoring is needed.
How do vets diagnose a mast cell tumor?
Diagnosis usually starts with a fine needle aspiration, where a small sample of cells is taken from the lump. This sample is reviewed under a microscope (cytology) to check for abnormal granules that are typical of mast cells. In some cases, a biopsy or full surgical excision of the tumor may be needed to remove and examine the entire tumor.
Why was my cat so itchy or nauseous before we even found the tumor?
Mast cell tumors can release histamine, which may cause itching, vomiting, or even allergic reactions. These symptoms often show up before a lump is visible. It’s the body’s way of reacting to the tumor and its effect on the immune system.
Can mast cell tumors spread to other parts of the body?
Yes. Some tumors can become metastatic, spreading to lymph nodes, internal organs, or even bone marrow. Your vet may recommend tests like abdominal ultrasound, blood work, or x-rays to check for signs of spread.
Is there any way to know if the tumor was high grade or more aggressive?
That’s where things like a biopsy and histopathology report come in. These tests examine the entire tumor and use a grading system to see how fast the cancer cells are growing. In cats, mast cell tumors don’t always fit into clear grading categories like they do in dogs. Still, biopsy results provide valuable insight into how aggressive the tumor may be and what to expect in terms of treatment and prognosis.
When is radiation therapy used for mast cell tumors in cats?
Radiation therapy is typically recommended when a cutaneous mast cell tumor cannot be fully removed with surgery or if surgical margins are incomplete. It may also be considered as a follow-up treatment to reduce the risk of recurrence. This approach is less common in cats than in dogs, but in select cases, it can improve long-term treatment outcomes.
Do cats with mast cell tumors need to see a veterinary oncologist?
Not always, but for complex or aggressive cases, especially visceral or metastatic mast cell tumors, your primary DVM may refer you to a veterinary oncologist. Specialists can offer advanced diagnostics, treatment plans, and options like chemotherapy or radiation therapy that aren’t available in general practice.
