These notes are provided to help you understand the diagnosis or possible diagnosis of cancer in your pet. For general information on cancer in pets ask for our handout "What is Cancer". Your veterinarian may suggest certain tests to help confirm or eliminate the diagnosis, and to help assess treatment options and likely outcomes.
Endocrine glands produce specialized chemicals called "hormones". These regulate and integrate many activities to maintain internal stability of the body.
Endocrine glands produce specialized chemicals called “hormones”. These regulate and integrate many activities to maintain internal stability of the body. The hormones pass directly into the blood to affect target cells elsewhere.
Dogs and cats have a pair of anal sacs, one located on each side of the anus between the external and internal anal sphincter muscles. The sacs are lined with modified sweat glands called anal glands.
A basal cell tumor is an abnormal growth/mass resulting from the uncontrolled division of basal cells. There is no known reason for the development of these tumors in cats and dogs; however, certain breeds of dogs and cats are more likely to develop basal cell tumors, including Wirehaired Pointing Griffons, Kerry Blue and Wheaten Terriers, Cocker Spaniels, Poodles, and Siamese Cats. Fine needle aspiration may aid to guide the diagnosis, but definitive diagnoses are typically made via surgical removal and histopathology. There are few reports of local recurrence and metastasis (spread) does not appear to occur. With adequate surgical removal, long-term control is likely.
Fibrous tumors, including hamartomas, are a group of benign tumors arising from fibrous and fibrous-like tissues. Nodular dermatofibrosis can be secondary to (or a consequence of) tumors in the kidney or uterus. Fibrous tumors can develop as the result of underlying, repeated trauma (e.g., pressure on the elbows when lying on hard surfaces and self-trauma with skin allergies). Therefore, once a diagnosis has been made, determining and understanding the underlying cause is important.
Mammary tumors in dogs are not very common in North America due to routine spay procedures. Hormones play a role in tumor development in dogs. Dogs spayed before their first heat have only a 0.5% chance of developing mammary tumors. Certain breeds appear to be predisposed to developing mammary tumors. Benign tumors are typically not painful and usually are discovered during routine examination by your veterinarian. Surgery is typically the treatment of choice.
Non-cancerous bone tumors are rare in cats and are mainly due to abnormal development. They include bone cysts and single or multiple lumps of bone in abnormal places (exostoses).
Chemodectomas are tumors of chemoreceptor cells located in several locations in the body, with the most common areas being the carotid artery and aorta. These tumors are considered rare in dogs, and especially rare in the cat. Brachycephalic breeds may be predisposed to developing these types of tumors. The most common clinical signs associated with aortic tumors include weakness/wobbliness, lethargy, collapse, exercise intolerance, increased respiratory rate and effort, fluid within the sac around the heart, cough, vomiting, and sudden death. The most common signs associated with carotid artery tumor are swelling in the neck region, regurgitation, lethargy, difficulty breathing, weakness, and collapse. Advanced imaging is typically used to diagnose these tumors. Surgery is the most common treatment option and pericardectomy may be recommended.
Chemotherapy is the therapeutic use of chemical agents to destroy, or inhibit the growth and division of cancer cells. Chemotherapy is usually used when tumors are widespread or when there is significant or immediate risk of spread from the primary location. It is often used following the surgical removal of tumors. In some cases, chemotherapy is started prior to surgery. Different protocols are used depending on the drug and the type of cancer being treated. The side effects of chemotherapy are related to the effects of chemotherapy on normal – as well as cancerous – cells. The principal goal with cancer care in pets is to provide cancer control without reducing quality of life. With pets, chemotherapy protocols are purposefully designed so the treatment does not become worse than the disease.