Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

C h a p t e r
TUMORS AND
CANCERS
A tumor is any sort of lump, bump, growth, or swelling. Tumors that are true
cancers are called neoplasms. Tumors can be divided into two broad categories:
benign and malignant. Benign tumors grow slowly, don’t invade or
destroy neighboring tissue, and don’t spread to other parts of the body. These
cancers aren’t usually life-threatening. They are cured by surgical removal,
provided that the entire tumor can be removed. Malignant tumors are potentially
life-threatening cancers, and are also called carcinomas, sarcomas, or
lymphomas, depending on the tissue where they originated.
Cancers invade neighboring tissue and continue to grow in an unrestricted
way. At some point, malignant cells part from the primary tumor and enter
the lymphatic system or the circulatory system, and establish new colonies in
other areas. This process is called metastasizing.
Any new growth on your dog should be examined by a veterinarian. The
majority of cancers in dogs are detected by physical examination. About half
are visible as growths or sores on or beneath the skin. Perianal tumors, testicular
tumors, mammary gland tumors, lymph gland tumors, and cancers in the
mouth can be detected by inspection and palpation. Bone tumors can be recognized
by a swollen limb, lameness, or the appearance of a swelling that
involves the bone.
Internal cancers are most common in the spleen, liver, and gastrointestinal
tract. Cancers in these areas often become advanced before they are even suspected.
Usually the first signs are weight loss, a palpable mass in the abdomen,
vomiting, diarrhea, constipation, or gastrointestinal bleeding. (The signs and
symptoms of common tumors affecting the internal organs are discussed in
the chapters dealing with these organs.)
Lung cancer is rare in dogs. However, dogs are at risk from secondhand smoke.
The lungs are also a frequent site for metastases. The same is true of the liver.
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