Cat & Dog - Sweat Gland Tumours

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. If not already performed your veterinary surgeon may suggest certain tests to help confirm or eliminate the diagnosis, and to help assess treatment options and likely outcomes. Because individual situations and responses vary, and because cancers often behave unpredictably, science can only give us a guide. However information and understanding of tumours in animals is improving all the time.

We understand that this can be a very worrying time and we apologise for the need to use some technical language. If you do not understand anything please do not hesitate to ask.

What is this tumour?

This tumour is a disordered and purposeless overgrowth of sweat gland cells. Most sweat glands are attached to the hair follicles (paratrichial) but a few are not associated with follicles (atrichial). Most sweat gland tumours are benign and can be permanently cured by total surgical removal. Malignant tumours that spread to other parts of the body are rare.

What do we know about the cause?

The reason why a particular pet may develop this, or any cancer, is not straightforward. Cancer is often seemingly the culmination of a series of circumstances which come together for the unfortunate individual.

We do not know precisely what causes these tumours. Induction of cancer is a multi-step process called tumour progression. The majority of sweat gland cancers never progress past the first stages and are technically hyperplasias (overgrowths) rather than true, out-of-control cancers. Hyperplasia and benign tumours (adenomas and complex adenomas) grade into each other.

Is this a common tumour?

The tumours are uncommon in both dog and cat. They are usually found in animals over six years of age but can occur earlier. Malignant tumours are rare and when they do occur tend to be in slightly older animals. They are slightly more common in cats than dogs.

On the eyelid, these tumours are frequently multiple. The proximity of the eye makes full excision difficult.

How will this cancer affect my animal?

These tumours are usually noticed as lumps and the main problems are physical because of the size and sites. They are often cystic and may ulcerate and bleed or become secondarily infected. Tumours may be painful if they have ruptured because sweat is irritant.

The malignant tumours (adenocarcinomas) are locally aggressive. Distant metastasis only occurs after some time. It is more likely to occur in cats than dogs.

How is the tumour diagnosed?

Clinically, these tumours resemble other tumours of the skin. They may be dark in colour so can be mistaken for other tumours. Diagnosis relies upon microscopic examination of tissue. Needle aspiration for microscopic examination of cell samples (cytology) may be helpful for rapid or preliminary tests but is less diagnostic than histopathology. Histopathology is the microscopic examination of specially prepared and stained tissue sections. This is done at a specialised laboratory where the slides are examined by a veterinary pathologist. The information from this examination also enables more accurate prediction of behaviour (prognosis) and a microscopic assessment of whether the tumour has been fully removed. Histopathology also rules out other cancers.

The diagnosis includes words that indicate whether a tumour is 'malignant.  Malignancy is often shown by the word ending 'carcinoma'.

What treatment is available?

Treatment is surgical removal of the lump. If this is then sent for histopathological diagnosis, the diagnosis can be confirmed, the completeness of excision assessed and other diagnoses ruled out.

Can this cancer disappear without treatment?

Cancer very rarely disappears without treatment. Very occasionally, spontaneous loss of blood supply to the cancer can make it die but the dead tissue will still need surgical removal. The body's immune system is not effective in causing this type of tumour to regress.

How can I nurse my pet?

Preventing your pet from rubbing, scratching, licking or biting the tumour will reduce itching, inflammation, ulceration, infection and bleeding. Any ulcerated area needs to be kept clean.

After surgery, the operation site similarly needs to be kept clean and your pet should not be allowed to interfere with the site. Any loss of sutures or significant swelling or bleeding should be reported to your veterinary surgeon. If you require additional advice on post-surgical care, please ask.

How will I know if the cancer is permanently cured?

'Cure' has to be a guarded term in dealing with any cancer.

Histopathology will give your veterinary surgeon the information that will help to indicate how the tumour is likely to behave. The veterinary pathologist usually adds a prognosis that indicates the probability of local recurrence or metastasis (distant spread).

Hyperplasias and benign tumours can be cured by surgery. The rare malignant tumours can usually be cured surgically as well as metastasis is unusual and rarely occurs at an early stage of the cancer.

Are there any risks to my family or other pets?

No, these are not infectious tumours and are not transmitted from pet to pet or from pets to people.