Continued from last week

We have already established that there are several types of skin cancer which can affect dogs/cats. It is important to differentiate them from benign tumours, such as some of those discussed in previous columns. In some cases, it is difficult to decide whether a tumour is a benign or a malignant cancer, just on the basis of appearance alone. Surgical removal of a part of the lump or bump followed by laboratory examination of the tissues may be required to establish the correct diagnosis. My position has always been that if the lump is small, then the vet should excise the whole lump and send it for laboratory diagnosis. Why wait?

The following skin tumours are common in the dog. Although they are not invariably malignant, all have a malignant potential:

Sebaceous gland adenomas

Sebaceous glands are tiny glands which are found alongside each hair. These glands secrete an oily substance which serves to keep the hair from becoming too brittle and which gives the animal’s hair that glossy appearance. Sebaceous adenomas are relatively common adenomas especially in older dogs/cats. They arise from oil-producing skin glands. Cocker Spaniels seem to be affected more often than other breeds. These adenomas (an adenoma is simply defined as a benign swelling of a gland or gland-like structure) are light-coloured, usually less than an inch long, and present a cauliflower-like appearance. The surface of the skin may be ulcerated. About 25 per cent are low-grade cancers. Large adenomas should be removed. They are more likely to develop into genuine cancers.

 Mast cell tumours

pet cornerMast cell tumours of the skin are also called mast cell sarcomas. Any time you read/hear the word ‘sarcoma,’ you must think of genuine cancer. These types of tumour are the most frequently recognized malignant or potentially malignant growths in dogs. Mast cell tumours are common in older dogs. They are prevalent in Boxers and Boston Terriers. The average dog with a mast cell tumour is about eight years old. Look for these tumours on the hind legs, lower abdomen and prepuce (foreskin of the penis).

Typically, they are multi-nodular growths less than an inch in length. Some of these growths can become malignant. Cancer is more likely when growth is rapid and the size is greater than one inch. Pieces of malignant mast cell tumours can break off from the parent mass and, via the bloodstream, be transported to and lodge themselves in distant organs.

Cortisone therapy may be introduced to decrease temporarily the size of mast cell tumours, but the treatment of choice is surgical removal.

Epidermoid carcinoma

An epidermoid carcinoma is a cauliflower-like mass of tissue or a hard flat grayish looking ulcer that does not heal. Its size is variable. It occurs mostly on the feet and legs, and sometimes elsewhere. Hair may be lost around the tumour due to constant licking. This tumour is malignant and should be removed.


A melanoma is a malignant mass of tissue which takes its name from the brown or black pigment usually associated with it. Often it develops in a pre-existing mole. You should suspect melanoma when a mole starts to enlarge or spread out, becomes elevated above the surface of the skin or starts to bleed. Melanomas are more common in Scottish Terriers, Boston Terriers and Cocker Spaniels.

Any suspicious mole should be removed. Discuss the problem with your vet. Melanomas spread widely, often at an early stage.


Histiocytomas are rapidly growing button-like tumours that occur in younger dogs. They are to be found most commonly on the feet, face and ears. In appearance, they are dome-shaped, raised, red, irritated-looking and painful to the touch. Some histiocytomas become smaller and disappear on their own in a few weeks. Others may need to be removed.

Next week we will continue with some more types of surface cancers. Although it is a tedious exercise, we must deal with them since our canine and feline wards can become afflicted therewith from time to time.

Please implement disease preventative measures (vaccinations, routine dewormings, monthly anti-heartworm medication, etc) and adopt-a-pet from the GSPCA’s Animal Clinic and Shelter at Robb Street and Orange Walk, if you have the wherewithal to care well for the animals.  Do not stray your unwanted pets, take them to the GSPCA’s Clinic and Shelter instead. If you do not wish your pet to have puppies or kittens, you may exploit the GSPCA’s free spay and neutering programme. If you see anyone being cruel to an animal, or if you need any technical information, please get in touch with the Clinic and Shelter by calling 226-4237.



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