Papillomas
of the Skin
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 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 about tumors and their treatment in animals is improving all the
time.
This can be a very worrying time. If
you have any questions please do not hesitate to ask your veterinarian.
What
is a papilloma of the skin?
Papillomas are benign, sometimes multiple, tumors caused by viruses.
They are commonly known as "warts". The tumors often disappear
spontaneously because the animal slowly develops immunity to them. Some
papillomas may need to be removed surgically because they have become inflamed
or infected, or bleed. They are permanently cured by total surgical removal and
do not spread to other parts of the body, although there may be multiple
tumors.
A squamous papilloma
resembles a viral papilloma, but is without evidence of viral infection.
What
do we know about the cause?
The reason why a particular pet may
develop this, or any tumor, is not straightforward. Cancer is often the
culmination of a series of circumstances that come together for the unfortunate
individual.
After invading the cells, papilloma
viruses insert their genetic information into the host cell's DNA (nucleic
acid) and upset the normal regulatory mechanisms of cell division, so that the
cell divides abnormally and more frequently. The virus activates
growth-promoting genes in the DNA (oncogenes), at the same time it inactivates
suppressor genes that would normally limit cell proliferation and alters the
genes that regulate normal, programmed cell death.
There are many different types of
papilloma virus and they occur in all species of animals, including people. Each
species of animal has its own viruses and their related tumors. One of the best
known is the verruca of human feet (plantar wart).
Why
has my pet developed this tumor?
Your dog or cat has been infected
with one of these papilloma viruses. Normal animals and people carry many
viruses asymptomatically (without any clinical signs). Over 130 subtypes of
papilloma virus have been identified in people and eighty of these have been
fully gene-sequenced. However, we know little about canine and feline papillomaviruses.
Only two subtypes have been fully characterized in the dog and two subtypes are
recognized in cats.
"Papilloma viruses... can
survive for long periods in the environment."
Sometimes the viral infection is
recent but in other cases, the immune system in an infected animal becomes less
competent for some reason. In these cases, a papilloma virus that has been
carried by that animal for a long time is then able to induce tumors. Papilloma
viruses are very resistant to adverse conditions so can survive for long
periods in the environment outside an animal. They gain access to the body when
the skin becomes softened by moisture, through cuts and abrasions, or with the
assistance of ticks or biting insects (fleas, mosquitoes, et cetera).
Is
this a common tumor?
Papillomas are uncommon in cats but
common in dogs. Clinical syndromes include multiple oral (mouth) papillomas in
young dogs, solitary cutaneous (skin) papillomas in dogs of any age, venereal
(genital) papillomas, eyelid or conjunctival papillomas and fibropapillomas.
There are probably different viruses associated with different sites and in
young and old animals.
In dogs, we see most of these tumors
on the feet, or around and in the oral cavity.
Skin papillomas in cats are usually
flat and plaque-like (sometimes scaly). There is also a fibropapilloma or
sarcoid in cats caused by a special subtype of papilloma virus.
How
will this tumor affect my pet?
The lesions are usually inflamed
polyps ("warts"), but they may be flat, scaly plaques or inward growing
hard masses. They may ulcerate or bleed. The inward growing ones may cause
pain, particularly if they are on the feet.
There may be some genetic subtypes
of animals who fail to recognize viral protein antigens. In these animals,
immunity cannot develop and the tumors persist. We do not know about
genetically determined immunity in dogs - but some dogs have persistent tumors.
Some viral papillomas in man are associated with cancer and papilloma viruses
have been found in feline cancers (squamous cell carcinoma).
How
is this tumor diagnosed?
Clinically, most papillomas of the
skin have a typical appearance, although the more common sebaceous tumors of
dogs are very similar. Definitive diagnosis relies upon microscopic examination
of the tumor. To obtain suitable samples of the tumor, your veterinarian may
recommend one or more sampling techniques such as needle aspiration, punch
biopsy and full excision of the tumor. Cytology is the microscopic examination
of cell samples. This is used for rapid or preliminary screening tests, but
accurate diagnosis usually requires microscopic examination of tissue
(histopathology). Your veterinarian will submit the appropriate samples to a
specialized laboratory where a veterinary pathologist will evaluate the tumor samples,
make a diagnosis and predict the prognosis. Histopathology also rules out other
diseases including more serious cancers.
What
types of treatment are available?
Some of these tumors regress
spontaneously but the usual treatment is surgical removal.
In humans, a topically applied
immune-modifying agent that stimulates interferon production has successfully
been used to treat papilloma virus lesions. It may have potential use in
animals.
Can
this tumor disappear without treatment?
Yes, the body's immune system can
cause this type of tumor to regress in time (weeks to months).
How can I nurse my pet?
Preventing your pet from scratching,
licking or biting the papillomas will reduce itching, inflammation, ulceration,
infection and bleeding. Any ulcerated area needs to be kept clean.
After surgery, you will need to keep
the incision site clean and dry, and prevent your pet from by rubbing, licking,
biting or scratching at it. Report any loss of sutures or significant swelling
or bleeding to your veterinarian. If you require additional advice on
post-surgical care, please ask.
When
will I know if the tumor is permanently cured?
'Cured' has to be a guarded term in
dealing with any cancer.
The histopathology report will give
your veterinarian the diagnosis that helps to indicate how it is likely to
behave. The veterinary pathologist usually adds a prognosis, which describes
the probability of local recurrence or metastasis (distant spread).
In healthy animals, the tumor is
usually cured by surgery. If the viral infection persists because an animal has
incomplete immunity, further tumors may develop. Rarely, the same site is
affected by repeated re-growth of the tumor.
Are
there any risks to my family or other pets?
"Although this is an infectious tumor, the viruses are
species specific and not transmissible to humans."
No, although this is an infectious
tumor, the viruses are species specific and not transmissible to humans. The
tumors in dogs, cats and people are not related nor are they transmitted
between species.
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This client information sheet is
based on material written by: Joan Rest, BVSc, PhD, MRCPath, MRCVS
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For Max’s
demodex, Dr. Shapiro prescribed oral medication which, while treatment would
span several weeks, started the healing process immediately. However the ulcer
in Max’s right eye would prove to be more challenging. The viral papillomas
growing on his face were too close to his eyes and were obstructing the ulcer
and causing additional irritation. With no room for medication to access the
area, no healing was possible. Max was
in need of some intensive care. But,
before that could begin, the papillomas had to be addressed. 
