Cancer is one of the leading health concerns for older pets. As dogs and cats age, the risk of developing cancer increases significantly—especially for dogs over the age of 10. According to the American Veterinary Medical Association (AVMA), nearly 50% of dogs over 10 years old will be diagnosed with some form of cancer.

Early detection is critical. Identifying symptoms early and understanding your treatment options can dramatically improve both the outcome and your pet’s quality of life. At Star of Texas Veterinary Hospital, we’re committed to walking with you through every step—offering guidance, care, and support for you and your pet.

Understanding Cancer in Pets

Cancer occurs when cells grow abnormally and uncontrollably. These cells may form a tumor (mass), or they may affect systems like blood or lymph. Not all tumors are cancerous:

  • Benign tumors are non-cancerous and usually grow slowly, without spreading to other organs.
  • Malignant tumors are cancerous, aggressive, and capable of metastasizing, or spreading to other parts of the body.

While some cancers are easy to detect, others are hidden deep within the body and may show subtle signs at first. Routine veterinary visits are essential for early detection.

Common Types of Cancer in Pets

Lymphoma

A cancer of the lymphatic system, lymphoma can affect lymph nodes, the spleen, and internal organs.
Symptoms: Swollen lymph nodes (especially under the jaw or behind the knees), fatigue, weight loss.
Treatment: Primarily chemotherapy. Many pets tolerate it well and experience good quality of life during treatment.
Learn more from Cornell University’s lymphoma resource.

Hemangiosarcoma

An aggressive cancer of the blood vessels, often affecting the spleen, liver, or heart in dogs.
Symptoms: Sudden collapse, weakness, pale gums, internal bleeding.
Diagnosis: Ultrasound and biopsy.
Treatment: Surgical removal of the tumor, followed by chemotherapy.
More from Cornell Vet.

Mast Cell Tumors

One of the most common skin cancers in dogs, mast cell tumors can appear anywhere on the body.
Symptoms: Raised, itchy, or ulcerated lumps on the skin.
Diagnosis: Fine needle aspiration and biopsy.
Treatment: Surgery, often combined with radiation or chemotherapy.

Squamous Cell Carcinoma

A type of skin or oral cancer, particularly seen in cats exposed to sun or tobacco smoke.
Symptoms: Chronic mouth sores, swelling, difficulty eating, or facial deformity.
Risk Factors: Sun exposure, especially in light-colored cats.
Treatment: Surgery and/or radiation therapy.
 Read more from Cornell Feline Health Center.

Osteosarcoma (Bone Cancer)

A fast-spreading bone cancer commonly seen in large-breed dogs.
Symptoms: Persistent limping, swelling in limbs, pain.
Treatment: Amputation followed by chemotherapy is the standard approach.

Oral Melanoma

A cancer of the mouth or gums, often seen in senior dogs.
Symptoms: Bad breath, oral masses, bleeding, difficulty chewing.
Treatment: Surgical removal, often combined with radiation or immunotherapy.

Recognizing the Signs of Cancer in Pets

Being proactive and attentive to changes in your pet’s behavior or body is key to early detection. Common signs include:

  • Lumps or bumps that grow over time
  • Sudden weight loss or appetite changes
  • Sores that don’t heal
  • Persistent cough or difficulty breathing
  • Vomiting, diarrhea, or unexplained bleeding
  • Lethargy, weakness, or decreased interest in activity

This AAHA resource outlines more signs to monitor.

How Cancer Is Diagnosed in Pets

A proper diagnosis is crucial to determine treatment and prognosis. Diagnostic tools include:

Treatment Options for Cancer in Pets

Treatment depends on cancer type, location, and stage—along with your pet’s age and overall health.

Surgery

Often the first step for removing localized tumors. Ideal for skin cancers, oral tumors, and certain internal growths.

Chemotherapy

Used for systemic cancers like lymphoma or metastatic disease. Most pets tolerate it far better than people expect—often with few side effects.

Radiation Therapy

Effective for inoperable or deep-seated tumors (brain, spine, nasal cavity). May be used after surgery to eliminate residual cancer cells.

Immunotherapy and Targeted Therapy

Newer treatments that activate the immune system or target cancer cells specifically. Includes melanoma vaccines and monoclonal antibody therapies.

Palliative and Supportive Care

When a cure isn’t possible, palliative care focuses on managing pain, improving appetite, and enhancing quality of life.

Preventing and Detecting Cancer Early

You can’t prevent all cancers, but you can reduce your pet’s risk and improve outcomes with early detection:

  • Schedule annual or semi-annual checkups, especially for senior pets
  • Monitor for changes in behavior, appetite, lumps, or energy
  • Maintain a healthy weight and active lifestyle
  • Spay or neuter your pets to reduce the risk of certain reproductive cancers
  • Protect light-skinned pets from sun exposure, particularly on ears and noses

Routine screenings and prompt attention to abnormalities give your pet the best chance for successful treatment.

Cancer is never easy to face—but it’s not always a death sentence. Many pets with cancer go on to enjoy many more months, or even years, of happy life with the right treatment and care.

If you’ve noticed a new lump, change in behavior, or anything that concerns you, contact Star of Texas Veterinary Hospital. Our team is here to help with clear answers, expert care, and a compassionate, realistic approach to your pet’s health.

Let’s work together to support your pet—because they deserve the best, through every stage of life.