malignant tumours

Last month we looked at some of the common benign tumours that can occur in your dogs skin. This month we are going to find out about the most common … (See last month’s article here)



This is one of the most common tumours found in the dog. Mast cells are special cells that are found throughout the body. They are responsible for the release of various active chemicals that help the body’s immune system respond to allergies and inflammation. When a mast cell becomes cancerous it releases excessive amounts of these chemicals causing damage to the tissues. The damage caused can result in gastric ulcers, internal bleeding as well as allergic reactions.

These tumours can occur anywhere on the body including the internal organs but are commonly found on the limbs, abdomen and chest. Some breeds such as Boxers, Pugs, Staffies and Ridgebacks are more susceptible to developing these tumours. 

The external appearance of the tumour can vary widely and biopsy is the only way to differentiate between the various types of this tumour. Surgical excision is usually the treatment of choice of depending on the type and grade of the tumour and how or if it has spread.


These tumours occur in the pigmented cells called melanocytes.

Only a small percentage of benign melanoma’s are found in the pigmented skin in areas that are covered with hair, most malignant melanomas are found in the mouth, mucous membranes, digit’s and scrotum area.

These are aggressive tumours that grow quickly and are very likely to spread to lymph nodes and internal organs such as the lungs and liver.

The incidence of malignant melanoma in certain breeds once again plays a role in the occurrence of this tumour.

Melanoma should be treated as soon as possible. Radical surgical removal of the tumour and surrounding tissue is absolutely necessary, in some cases this may result in amputation or removal of part of the jaw depending on the extent of the infiltration of the tumour.


This is a common skin cancer, which is often caused by excessive exposure to the sun. Dogs with very short coats ( and cats with white ears!) and light skin such as Bull Terriers, Dalmatians and Schnauzers are more likely to develop squamous cell carcinoma. Although this tumour is unlikely to spread to lymph nodes it is aggressive in its destruction of surrounding tissue.

Surgical removal is the treatment of choice if the tumour is situated in an operable place.

If you find a lump of any kind on your dog (or cat) seek veterinary advice. It is impossible for your veterinarian to make any diagnosis from an email or a picture on a clients cell phone of various lumps and bumps! However, in consultation your vet can examine your pet thoroughly, do a needle aspirate if necessary and upon these findings can advise you as to the correct method of treatment.

Chemotherapy and radiation therapy is available but it is debatable as to the efficacy of these treatments and the long-term benefits to your pet. All options can be discussed with your vet if you have concerns.

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