Understanding Cancer in Dogs & Cats: Symptoms, Causes, and Prevention
Summary: Cancer is sadly common in both dogs and cats, but early detection and informed care can make a big difference. In this guide, we outline the most common types of cancer in pets, what symptoms to watch for, treatment options, and how to reduce your pet's risk.
Jump to Section:
- Common Cancers in Dogs & Symptoms
- Common Cancers in Cats & Symptoms
- What Causes Cancer in Pets?
- Treatment Options
- How to Reduce Your Pet’s Risk
- Final Thoughts & Support
"I'm sorry, it's cancer."
Four of the most difficult words a pet parent can hear. We love our pets like family, and facing a cancer diagnosis can feel overwhelming. Unfortunately, cancer in pets is more common than many realize. In fact, up to 900 in every 100,000 dogs are diagnosed with cancer, and it’s responsible for nearly one-third of cat deaths.
Below, we’ll help you understand the most common types of cancer in pets, symptoms to look out for, what causes it, and how you can help protect your furry friend.
Common Types of Cancer in Dogs & Their Symptoms
There are over 100 types of cancer in dogs. Here are the most common:
Mast Cell Tumors: Skin lumps (may also affect internal organs). Common in breeds like Labs, Golden Retrievers, Boxers.
Melanoma: Dark or multi-colored spots, usually in or around the mouth. Seen in older dogs (10+), especially Poodles, Cockers, and Chows.
Lymphoma: Affects lymph nodes and organs like the liver or GI tract. Symptoms vary: swelling, vomiting, diarrhea.
Osteosarcoma: Bone cancer in large breeds (e.g. Rottweilers, Great Danes). Look for swelling, limping, or signs of pain.
Hemangiosarcoma: Affects blood vessels, often internal (spleen, liver). May cause belly swelling, lethargy, weight loss, or pale gums.
Common Types of Cancer in Cats & Their Symptoms
Lymphoma: Often linked to feline leukemia virus (FeLV). Look for swelling, weight loss, difficulty eating.
Squamous Cell Carcinoma: Sun-related skin cancer. Appears on nose, ears, eyelids—especially in pale or white cats.
Fibrosarcoma: Cancer of soft tissue. Often shows as a painless lump under the skin.
Mammary Cancer: More common in older, unspayed females. Small lump near nipple may spread quickly.
Additional symptoms to watch for include: increased thirst, frequent urination, anemia, or sudden appetite changes.
What Causes Cancer in Pets?
Some causes include:
- UV exposure (sunburn-related cancers)
- Second-hand smoke
- Pesticides, herbicides, and other chemicals
- Pollution and environmental toxins
- Genetic predisposition by breed
In unspayed females, hormones like estrogen and progesterone increase the risk of mammary cancer.
Treatment Options
Treatment depends on the type, location, and stage of the cancer. Common approaches include:
- Surgery: To remove tumors or affected limbs
- Chemotherapy: Often well-tolerated in dogs (no hair loss)
- Radiation: Used alongside surgery or on its own
- Immunotherapy: Boosts the immune system to fight cancer
- Stem Cell Therapy: For some blood cancers like leukemia
In some cases, your vet might refer you to a veterinary oncologist or suggest participation in clinical trials for new treatments.
How to Reduce Your Pet’s Risk of Cancer
- Spay or neuter your pet early—this greatly reduces risk of reproductive cancers
- Feed a high-quality, balanced diet
- Limit sun exposure, especially for light-skinned pets
- Never smoke near your pet
- Schedule regular vet check-ups, especially for senior pets
Early detection is key—don’t ignore lumps, changes in behavior, or unexplained symptoms.
Final Thoughts & Support
A cancer diagnosis isn't always a death sentence. With early detection and proper care, many pets go on to live full, happy lives. Treatment options are expanding every year, and many are well tolerated by pets. Work closely with your vet to make the best decisions for your pet’s comfort and wellbeing—and know that you're not alone in facing this journey.
