Lumps and Bumps: Common Pet Cancers

November 20, 2020
Lumps and Bumps: Common Pet Cancers
Cancer. The word strikes fear into the heart of every pet owner. No one wants to imagine their best friend having a possibly life-threatening disease, but as pets live longer, cancer is increasingly common. According to the American Veterinary Medical Association (AVMA), approximately 25% of all dogs, and almost half of dogs over 10 years old, will develop cancer at some point. Fortunately, advances in cancer diagnostics and research mean that there is a better chance of long-term remission so pets can enjoy many more healthy, happy years with their families. If your family veterinarian suspects that your pet has cancer, the Care Center’s oncology department and team of board-certified veterinary specialists can offer the most cutting-edge diagnostics and treatments, to give your pet the best chance of remission.  
Cancer treatments are most effective when administered early, before cancer can progress or spread. Monitoring your pet for early disease signs is the best way to detect a problem when treatments can be most effective and provide more quality time with your pet. Arming yourself with knowledge about common pet cancers can help you identify early warning signs in your pet.   

Lymphoma in pets

Lymphoma is a cancer of lymphocytes, a type of white blood cell that circulates in the blood and is located throughout body tissues, including the lymph nodes, spleen, liver, bone marrow, thymus, gastrointestinal (GI) tract, skin, and lungs. Lymphocytes are so widely distributed that lymphoma can affect almost any body part, and often affects multiple locations. Lymphoma is common in dogs and cats, causing up to 24% of all canine cancers, and ranking as the most common feline cancer. In cats, lymphoma most frequently affects the GI tract, and can develop secondary to feline leukemia infection.    
Since lymphoma can affect any body part, the cancer can present with a variety of signs, including:
  • Swollen lymph nodes, particularly under the neck, near the shoulders, and behind the knees
  • Lethargy
  • Decreased appetite
  • Vomiting and diarrhea, particularly in cats
  • Weight loss
  Lymphoma can be aggressive, but typically responds well to treatment, and can often be put into remission for months to years, providing pets and their owners with more valuable time together.   

Brain tumors in pets

A dog or cat can develop a tumor in any part of their brain, or the tissues surrounding the brain. Common brain tumors in pets include:
  • Meningiomas
  • Gliomas
  • Choroid plexus papillomas
  • Pituitary adenomas and adenocarcinomas
  Cancer that develops elsewhere in the body, such as lymphoma or hemangiosarcoma, can also spread (i.e., metastasize) to the brain.    A brain tumor can interfere with normal brain functions, because a particular brain part is involved, or pressure is placed on the brain from the space-occupying mass. Brain tumor signs in pets depend on the tumor type and location, but can include:
  • Ataxia and incoordination
  • Abnormal pupillary size 
  • Behavior changes
  • Seizures
  Brain tumors vary in their malignancy and aggressiveness. If your pet develops brain tumor signs, or your family veterinarian suspects a brain tumor, we can use magnetic resonance imaging (MRI) to confirm the diagnosis and devise a treatment plan. Brain tumor treatment may involve surgical removal, chemotherapy, conventional radiation therapy, or stereotactic radiosurgery.  Prognosis depends on the tumor type and location.   

Mast cell tumors (MCTs) in petsCommon Pets Cancers

MCTs are a cancer of mast cells, which are white blood cells containing granules that function in allergic and inflammatory reactions. MCTs are the most common skin tumor in dogs, usually developing in older dogs, and many breeds are predisposed, particularly boxers. MCTs can also affect cats.   MCTs appear as a lump on or under the skin, which can sometimes be hairless or ulcerated. They are often itchy, and become red and swollen when handled, when the mast cells release histamine granules.    A pathologist grades an MCT after surgical removal, as a needle biopsy does not provide sufficient information for a complete diagnosis. Aggressive MCTs are locally invasive, likely to spread, and carry a guarded prognosis, whereas surgical removal is typically curative for less aggressive MCTs.   

Osteosarcoma in pets

Osteosarcoma is the most common bone cancer type in pets, accounting for 95% of all bone tumors in dogs, and most commonly affecting large-breed dogs. Osteosarcoma is highly aggressive, typically invading and weakening nearby bone, often leading to a pathologic fracture, which is sometimes the first disease sign. Osteosarcoma also commonly spreads to the lungs. In addition to a fracture, signs include:
  • Bone pain
  • Lameness and limping
  • Weakness
  • Difficulty breathing
  Osteosarcoma carries a guarded prognosis, as metastasis to the lungs typically occurs by the time cancer is detected. Treatment involves amputation of the affected limb and chemotherapy, but is curative in fewer than 25% of cases. Additional treatment is aimed at controlling pain and providing a good quality of life during the pet’s remaining time. Osteosarcoma is less common in cats, and carries a better prognosis when local control can be achieved.   If your pet has a mysterious lump or bump, or has been acting abnormally, schedule an evaluation with your family veterinarian immediately. If cancer is suspected, contact the Care Center’s oncology department to discuss advanced diagnostic and treatment options that can offer your best friend the best chance of recovery.