The scientific word for cancer is neoplasia, meaning new growth. In reality, it is an abnormal growth of cells that interferes with an organ’s ability to function, resulting in a degree of failure in that organ.

Some of these abnormal cells break off from the organ and spread to other organs in the body, causing them to fail. This process is called metastasis, and is the hallmark of malignant cancer.

Later in this page are links to pages with details on the more common cancers in animals. This includes dogs and cats, canines and feline, along with birds and reptiles (avian and herps). There are very few species of animal that do not get cancer.

Cancer in animals is diagnosed in several different ways. The following are four of the more common methods:


The following two radiographs show malignant cancer in different dogs. One cancer is of the lymph nodes, the other is of the bone.

Xray of cancerous lymph nodes

The enlarged sub-lumbar lymph nodes in this dog’s abdomen are the whitish areas under the circle. A cancer called adenocarcinoma spread to them through the process of metastasis.

Xray of bone cancer

This is what severe bone cancer looks like on the front foreleg (radius and ulna) of a dog. It is a malignant cancer called osteosarcoma. Compare it to the normal radius and ulna below to see the signifiant bone destruction. 

Xray of normal dog forearm
A normal radius and ulna on a radiograph

Blood Panels

Anemia blood panel

This pet is anemic, as indicated by the low RBC, HGB, and HCT. Many different cancers can cause this. 

Elevated WBC count in blood

This pet has an elevated WBC count (leukocytosis) and elevated lymphocytes (lymphocytosis). A cancer called lymphoma or lymphosarcoma can cause this. 


Ultrasound of intestinal cancer

This canine has a cancer inside its intestines detected by ultrasound. 


These are biopsy reports taken from a skin lesion. The first is benign, the second is malignant. You cannot tell this just by looking at them.

Dog sebaceous adenoma biopsy

This sebaceous adenoma skin lesion is benign

Dog mast cell biopsy report

This mast cell tumor is malignant. 

Cancer it is not one disease, has many different causes, and can affect every organ. This makes it quite a challenge to diagnose and treat. Even though the cause is not known in many cases, we do know of major factors that predispose pets to getting cancer.

An example is squamous cell carcinoma (SCC) in white cats that are exposed to the sun. We also tend to see cancer more commonly in our geriatric patients.

A predisposing factor is canines, felines and rabbits that are not neutered (castrated) and spayed (OVH) when they are young.  Their chances of getting breast (mammary), testicular, and prostate cancer increase significantly when they are not altered at an early age.

The following pages have detailed information on a wide variety of cancer in animals:

Reproductive Cancers

Dog and Cat Non-Reproductive Cancers




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