common skin growths

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common skin growths

common skin
growths
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OVERVIEW
As they age, pets can develop several different types of benign growths in or just beneath the
skin. The most common growths are cysts, papillomas (warts), and fat tumors. These lumps are
generally slow-growing, but can sometimes become irritated or infected, or can interfere with
normal movement.
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Cysts are hollow sacs containing liquid or solid material. These usually appear as soft,
fluid-filled swellings under the skin that are not fixed, i.e., they can be moved around
within a small area.
Papillomas are benign skin tumors caused by viruses similar to those that cause human
warts. They are common in dogs (but not in cats), in which they usually show up as
inflamed polyps, often on the feet or around and in the mouth.
Lipomas are literally tumors made out of fat. These soft, painless masses generally lie
just under the skin and are freely movable.
There are also numerous but less common growths that arise from various skin tissues, such as
hair follicles, oil glands, and fibrous tissue.
In most instances, your veterinarian can make a tentative diagnosis based on a history and
physical exam. On occasion, he or she may use a needle and syringe to draw some fluid or a few
cells from the mass for microscopic examination. Sometimes X-rays may be recommended, or
your vet may surgically remove the whole tumor and send it for histopathology to confirm
the diagnosis.
Lumps that aren’t irritated or interfering with movement are often treated with “watchful
waiting” and periodic rechecks. In other cases, your vet may recommend removing the mass
using either a local or general anaesthetic. Fluid-filled cysts can be periodically drained, but the
material usually accumulates again over time. Minor irritation and infection can be treated with
cleaning and use of topical or, in extreme cases, oral antibiotics and corticosteroids.
This POD deals primarily with benign skin growths. There are malignant skin tumors, and it is
sometimes difficult to tell these from benign ones.
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THE SKIN
The skin is a large, intricate, and underappreciated organ. In fact, it is the largest organ of the
body, comprising 12%–24% of an animal’s body weight, depending on species and age. The skin
performs many important functions, including:
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Keeping moisture in and harmful organisms out
Protecting underlying tissues from the environment
Producing pigment and vitamins, especially vitamin D
Promoting sensory perception (i.e., the sense of touch)
The skin is divided into three layers: the epidermis, the dermis, and the subcutis.
The epidermis is the outermost layer of the skin and acts as a barrier to keep moisture in and
protect underlying tissues. It is made up of columns of cells called keratinocytes, which grow out
from a basement membrane that separates the dermis from the epidermis. As these cells migrate
outward, they die off so that the dead cell bodies form a layer of waxy tissue called the stratum
corneum. This outermost part of the epidermis is the main barrier that protects underlying tissues
and stops water, salt, and mineral losses through the skin. The stratum corneum also prevents
infectious agents from entering the deeper parts of the epidermis, which contain immune cells to
combat organisms that do manage to get past the stratum corneum.
The dermis lies between the epidermis and underlying tissues, such as fat and muscle. It contains
the blood vessels that nourish the skin, the nerves that allow sensation and motor function (e.g.,
erector muscles that stand hair on end when needed for warmth), the hair follicles that produce
the fur, and oil (sebaceous) glands. The dermis also provides nourishment and hormonal control
for the epidermis.
The subcutis (also known as the hypodermis) is the layer of fat and blood vessels that lies below
the skin and atop underlying muscles and bones.
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THE SKIN
Diagram of the skin and associated structures
Source: Case, Linda P. Canine and Feline Nutrition: A Resource for Companion Animal Professionals,
3rd Edition. Elsevier, 2011. Copyright Proctor and Gamble Co., Cincinnati, Ohio, 2009.
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CYSTS
The most common cysts are the follicular and apocrine sweat-gland varieties, but congenital
cysts can also form during fetal development, and traumatic cysts can form as a result of
irritation or skin damage (similar to blisters or boils).
Cysts are typically not painful. But they can occasionally rupture, resulting in infection and
inflammation in the area.
Follicular (Epidermal-Inclusion) Cysts
These growths consists of a sac lined with epithelial cells that exude the cyst contents. They are
uncommon in cats but common in dogs, especially in middle-aged animals of certain breeds,
including Boxers, Shih Tzus, Schnauzers, and Basset Hounds.
These cysts are most commonly found on the head, body, or upper limb area in dogs, and on the
head, neck, or body in cats.
Follicular cysts are usually solitary, well-circumscribed growths that are either firm or fluctuant
to the touch. They typically measure 0.5 to 5 cm (usually <2 cm) in diameter, sometimes with
hair loss. The cystic lesion may become inflamed or secondarily infected, which can make them
painful or itchy. When handled, cysts may rupture and ooze a thick gray to yellow-brown
purulent material.
Example of typical follicular cyst in the dog
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CYSTS
Examples of typical follicular cysts in the dog, continued
Source: Hnilica KA. Small Animal Dermatology: A Color Atlas and Therapeutic Guide, 3rd Edition.
Elsevier, 2011.
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CYSTS
A follicular cyst that has ruptured
Elsevier, 2011.
Follicular cyst before being drained with a needle and syringe
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CYSTS
Follicular cyst after being drained with a needle and syringe
Elsevier, 2011.
Apocrine (Sweat-Gland) Cysts and Tumors
Cysts can sometimes develop from around sweat glands, although these lesions are not as
common as follicular cysts. Benign tumors involving sweat glands produce similar types of
cysts. Most sweat-gland cysts/tumors develop in older animals, especially German Shepherd and
Golden Retriever dogs.
Dogs
In dogs, apocrine cysts look like raised, round, fluctuant nodules within the layers of the skin.
They typically measure 0.5 to 3.0 cm and contain a clear fluid. They are found most commonly
on the head.
Apocrine tumors are usually solitary, raised, hairless, well-defined masses that form in or under
the skin. They may have a bluish tint. These tumors can be firm or fluctuating, or they may
ulcerate, leaving a reddened crater. Benign apocrine tumors range in size from 0.5 to 4 cm in
diameter and can develop anywhere on the body.
Cats
Cats (especially Persians and Himalayans) can sometimes develop multiple apocrine cysts, often
on the eyelids. These small cysts typically measure 2 to 10 mm in diameter.
Feline apocrine tumors are usually solitary, well-circumscribed, raised, firm or fluctuant lumps
ranging from a few millimeters to a few centimeters in diameter. These tumors appear most
commonly on the head, can have a bluish tinge, and may ulcerate.
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CYSTS
Typical apocrine tumor (top) and cyst (bottom)
Elsevier, 2011.
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CYSTS
Diagnosis, Treatment, and Prognosis
Your vet can often diagnose a cyst just by examination, but he or she may recommend drawing
some fluid from it with a needle and syringe. A sample of the fluid can be sent to the laboratory
or examined under the microscope to identify the type of cyst. A biopsy may be needed to
definitively confirm the diagnosis.
Treatment may initially consist of watchful waiting, with further therapy only if the cyst
becomes infected or otherwise bothersome. You should never try to manually squeeze out the
contents of a cyst because serious infection can develop if this material ruptures under the skin.
Your vet may be able to drain the cyst, but the lump typically re-fills again.
Infected cysts can be treated with antibiotics, but surgery to remove the cyst is generally needed
to prevent it from recurring. Other treatments may be necessary if there is a primary or
underlying cause for the cyst. Cysts caused by trauma usually resolve with time after the
damage heals.
The prognosis is good because cysts are benign, noncancerous growths that can be completely
removed by surgery. However, apocrine tumors may sometimes recur after surgery and rarely
can spread to other sites.
LIPOMAS
Many benign tumors in animals originate from fat (adipose) tissue and are called lipomas. They
are extremely common in dogs but rare in cats. Lipomas can occur in any middle-aged to older
dog, but are especially common in Dobermans, Labradors, Miniature Schnauzers, and
overweight dogs.
These fatty lumps can be found anywhere on the body, but are most common on the chest,
abdomen, and limbs. Most grow slowly and are benign, so that they do not spread to other parts
of the body.
Lipomas usually show up as one or more well-circumscribed, soft to firm masses under the skin.
They are typically 1 to 30 cm in diameter and can be easily moved with hand pressure. Less
commonly, lipomas can take the form of large, soft, poorly circumscribed masses that infiltrate
underlying muscle, tendons, and connective tissue.
Lipomas are not painful and cause no hair loss or redness. They rarely cause any discomfort at
all unless they are very large or interfere with the dog’s movement because of location (e.g., over
a joint).
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LIPOMAS
Most can be readily diagnosed during a physical exam, but your vet may use a needle and
syringe to withdraw a small sample of cells for examination under the microscope. In some
cases, a biopsy may be needed to confirm the diagnosis, with a sample sent to the lab when the
mass is removed. Surgical removal is curative but generally not necessary unless the lipoma
interferes with your pet’s movement.
Typical Lipoma
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LIPOMAS
Typical Lipoma
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LIPOMAS
Typical lipoma
Source: Hnilica KA. Small Animal Dermatology: A Color Atlas and Therapeutic Guide, 3rd Edition. Elsevier, 2011.
PAPILLOMAS
Papillomas, or warts, are benign skin tumors caused by viruses. These papillomaviruses are
transmitted by direct or indirect contact among dogs (through toys, bedding, etc.).
Papillomaviruses can survive for long periods of time in the environment before entering the
body through cuts, scrapes, insect bites, or areas of inflammation. Young pets or those with
depressed immune function (e.g., cats with feline immunodeficiency virus [FIV]) are
most susceptible.
The warts usually take 1–2 months to develop, and can regress spontaneously after 4–6 months
(mouth) or 6–12 months (skin). In dogs, they usually show up as inflamed polyps, often on the
feet or around and in the mouth. They may also appear as flat, scaly, raised areas called plaques,
or as hard masses that grow inward. Any of these lesions may ulcerate or bleed, and the type that
grows inward may be painful, particularly if they are on the feet.
Papillomas are less common in cats, in which they are usually flat and sometimes scaly.
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PAPILLOMAS
There are many different varieties of papilloma viruses, with each species of animal (including
people) infected by different types. Because each species has its own viruses, there is little
danger of your pet transmitting a papilloma virus to you or other family members.
These viruses are carried by healthy animals without any signs of a problem, but can later cause
warts when the immune system is weakened by disease, malnutrition, or other factors.
Canine Warts
There are at least five types of papillomaviruses common in dogs, and these lead to slightly
different types of warts.
Canine oral papillomatosis is seen mostly in young dogs. The warts show up usually on the
mouth and lips but may occasionally appear on the nose, conjunctiva, or hairy parts of the skin.
Initially, the warts are multiple smooth white pimples or plaques, but progress to ridged,
cauliflower-like bumps. Most cases resolve on their own within a few months.
Canine cutaneous papillomas are typically seen in older dogs, especially Cocker Spaniels and
Kerry Blue Terriers. The warts generally afflict the head, eyelids, and feet. There may be one or
more bumps, which can be flesh-colored or pigmented. The warts are usually pedunculated,
hairless, smooth to wrinkly masses that typically measure less than 0.5 cm in diameter.
Cutaneous inverted papillomas are also seen mostly in young dogs. The warts are commonly
found on the belly and inguinal area. These single or multiple bumps are usually round, raised,
and pedunculated, measuring 1–2 cm in diameter. Like many types of warts, they frequently
clear up on their own after several months.
Multiple pigmented plaques occur commonly in young adult Pugs and Miniature Schnauzers,
possibly due to an inherited genetic trait. These plaque-like lesions can be found mostly on the
belly and mid thigh. They begin as pigmented bumps and plaques that progress to scaly, flaky,
flat masses. These growths do not regress on their own and may progress to cancerous lesions.
Canine genital papillomas are a relatively rare form of genital warts that cause raised, plaquelike
lesions on the penis or vaginal area.
Canine footpad papilloma is a relatively rare problem of adult dogs that may or may not have a
viral cause. The lesions are firm, horny masses on more than one footpad. Lesions between the
toes have been seen in Greyhounds. This problem may lead to lameness, especially if lesions are
infected or otherwise inflamed.
Feline Warts
Although warts are less common in cats, there are at least three types of feline warts.
Feline oral papilloma infection causes multiple raised, oval, small (4–8 mm) flat-topped masses
in the mouth, especially on the underside of the tongue.
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PAPILLOMAS
Feline multiple viral papilloma involves multiple variably sized (3 mm to 3 cm) masses that
progress from discolored areas to scaly plaques, primarily on the hairy skin of the head, neck,
back, belly, or upper limbs. This disease, which occurs mostly in middle-aged or older cats, can
sometimes progress to malignant cancer.
Feline solitary cutaneous papilloma is a rare type of wart that may not be caused by a virus.
A presumptive diagnosis is usually based on history and physical exam, but a skin biopsy is
needed to definitively confirm warts.
Most papillomavirus infections regress spontaneously after the pet’s immune response fires up to
deal with the problem. Several other treatments are available to speed up the process or to deal
with warts that become infected or fail to regress on their own.
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Single lumps can be surgically removed, but care must be taken not to seed the virus to
adjacent tissues during surgery.
Lumps can be frozen off (cryotherapy) or burnt off with a laser. These methods are
typically effective, but may need to be repeated.
Medical treatment can sometimes speed the regression of warts:
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The antibiotic azithromycin has shown occasional success at causing wart
regression.
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Anecdotal reports suggest that the immune-stimulating drug interferon may
remove warts if given 3 times weekly for 4–8 weeks (or 2 weeks beyond clinical
cure).
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It has also been suggested that other immune-stimulating drugs (e.g., levamisole,
thiabendazole) may be of benefit.
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Anecdotal evidence also supports the use of topical treatments such as imiquimod
cream or certain anticancer drugs. An Elizabethan collar should be placed on the
animal to prevent licking and ingestion of the medication. Owners should wear
latex gloves when applying the material.
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A genetically modified vaccine against canine oral papillomavirus shows promise
in refractory cases. This vaccine, produced by Georgetown University Medical
Center, caused regression of refractory oral papillomas in one dog treated for
several months.
o
Oral retinoid drugs used to treat psoriasis and other skin conditions have been
reported to be beneficial in one case each of canine inverted papilloma and canine
pigmented plaques.
Preventing your pet from scratching, licking, or biting the wart will reduce itching,
inflammation, ulceration, infection, and bleeding. Any ulcerated area should be kept clean.
The prognosis for papillomas is usually good, because the papillomas regress spontaneously in
most cases. However, in rare cases, certain lesions can become malignant.
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PAPILLOMAS
The typical wart-like features of canine papilloma virus
Elsevier, 2011.
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PAPILLOMAS
Papillomas sometimes show up as spread out, crusty plaques.
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PAPILLOMAS
Papillomas sometimes show up as spread out, crusty plaques, continued
Elsevier, 2011.
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OTHER BENIGN SKIN GROWTHS
Although not as common as cysts, warts, and lipomas, a variety of other benign skin growths can
be found on dogs and cats.
Intracutaneous Cornifying Epithelioma
This benign tumor of the hair follicle is relatively uncommon in dogs but can occur as solitary
nodules in any age or breed. Multiple nodules sometime occur, most commonly in young male
Norwegian Elkhounds and Keeshonds. Nodules appear as firm or fluctuant, well-circumscribed,
0.5–4 cm lumps in or just under the skin. Most have a variably sized, central pore from which
gray-brown crusty material can be expressed. Large pores may contain a hard, hornlike plug.
Intracutaneous cornifying epitheliomas are small, crusty nodules atop an underlying growth.
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Intracutaneous cornifying epitheliomas are small, crusty nodules atop an underlying growth.
Hair-Follicle Tumors
Several other benign tumors arise from hair follicles. These vary somewhat by appearance, body
location, and types of animal affected, but otherwise have similar characteristics and treatments.
Trichoepithelioma is uncommon in cats but relatively common in dogs, especially middle-aged
to older Basset Hounds, Golden Retrievers, German Shepherds, Miniature Schnauzers, Standard
Poodles, and Spaniels. Tumors usually occur as single (often multiple in Bassets), hairless, firm,
white-to-gray, multi-lobed masses that may ulcerate. They range in size from 1 mm to 2 cm
or more.
Pilomatrixoma is uncommon in dogs and very rare in cats, occurring primarily in pets 5–10 years
of age, especially Kerry Blue Terriers, Poodles, and Old English Sheepdogs. Tumors are solitary,
often hairless, firm, sometimes ulcerated or hardened, well-circumscribed masses in or under the
skin. These masses occur mostly on the body, are usually 1–10 cm in diameter, and can be domeshaped
or plaquelike.
Trichoblastoma is uncommonly seen in middle-aged dogs and cats, especially Poodles and
Cocker Spaniels. Tumors range from 1 to 2 cm, and appear as solitary, firm, dome-shaped,
hairless nodules most commonly found on the head and neck in dogs and on the front of the body
in cats.
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Tricholemmoma is rare in dogs and cats but sometimes occurs in animals 5–13 years of age,
especially Afghan Hounds. Tumors range from 1 to 7 cm and appear as firm, circumscribed
nodules, often on the head and neck.
Trichofolliculoma is rare in dogs and cats, with no known predilection by age, breed, or body
site. Tumors occur as solitary, dome-shaped nodules that may have a central depression or
opening that contains hair or greasy material.
Dilated pore of Winer is uncommonly seen in older cats, usually as a small (<1 cm), solitary,
firm mass or cyst with a central waxy or horny opening. Nodules are most common on the body,
head, and neck.
Example of hair-follicle tumor
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Various examples of hair-follicle tumors
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Various examples of hair-follicle tumors
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Sebaceous-Gland Tumors
These benign growths arise from oil glands in the skin. They are common in older dogs,
especially the following breeds:
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Poodles
Cocker Spaniels
Miniature Schnauzers
Terriers
Shih Tzus
Lhasa Apsos
Siberian Huskies
Irish Setters
Such tumors are uncommon in older cats, except for maybe Persians. On rare occasions, these
tumors can turn malignant in some dogs, especially Cocker Spaniels.
Sebaceous gland tumors occur most commonly on the body, legs, head, and eyelids in dogs, and
on the head in cats. They usually appear as solitary, firm, elevated, wart-like or cauliflower-like
growths that range from a few millimeters to several centimeters in diameter. They can be
yellowish or pigmented, hairless, oily, or ulcerated. Some nodular forms appear as
multiple growths.
Examples of sebaceous gland tumors. The appearance of these tumors can include
pigmented, ulcerated, and waxy forms.
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Fibroma
A fibroma is a benign tumor of the fibrous connective tissue of the skin. It is uncommon but can
occasionally be seen in middle-aged to older cats and dogs, especially Boxers, Golden
Retrievers, and Doberman Pinschers.
These usually show up as solitary, well-circumscribed, firm, dome-shaped or pedunculated
masses that range from 1 to 5 cm in diameter. Fibromas can occur anywhere on the body but are
most common on the limbs and flanks.
Typical fibroma
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Typical fibroma
Histiocytoma
This tumor is formed from immune cells called histiocytes. Histiocytomas are commonly found
on young dogs and rarely on cats. Most appear on the head, ear, or legs.
These solitary, firm, 0.5–4-cm lumps often grow rapidly and appear red, angry, or ulcerated,
making people think they are malignant. However, they are actually quite benign and tend to
regress on their own in a few months.
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Various examples of canine histiocytomas
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Skin Tags
Just like people, dogs can sometimes develop skin tags as they grow older. The condition is rare
in cats and relatively uncommon in dogs, except for large and giant breeds.
These 1–2-cm, worm-like tags form out of fibrous and vascular tissue in the skin, possibly as a
response to repetitive trauma. They are most common on the chest, body, and bony points such
as the elbow. Most cause no problem, although the larger ones can ulcerate.
Skin tag on a dog
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Your vet can usually make a presumptive diagnosis based on history, physical exam, and perhaps
a skin scraping. Histopathology is needed for definitive diagnosis.
Often, watchful waiting is a reasonable course of action when dealing with benign skin tumors.
However, removal with a scalpel, laser, or cryosurgery usually cures them, and is a good option
for ugly or bothersome lesions, or when there is concern about possible malignancy.
In the case of intracutaneous cornifying epithelioma, single lesions can be cured with surgery,
but medical therapy with either oral vitamin A or retinoid drugs is often a better choice for
multiple masses. Medical treatment can be fairly effective at clearing up lesions but does not
work in all dogs. Dogs that do respond to medication typically require lifelong therapy to
maintain remission.
Prognosis is generally good for all these benign tumors, given that they do not metastasize and
rarely recur. In the case of multiple hair-follicle tumors, new growths sometimes develop at other
sites. In the rare case of a malignant sebaceous gland tumor, surgical excision must be complete
to prevent the growths from invading adjacent tissues or nearby lymph nodes.
A laser being used to remove multiple sebaceous-gland tumors
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SIGNS OF MALIGNANCY
Throughout this POD, we’ve frequently told you that watchful waiting is a reasonable approach
for dealing with many skin growths. So, it is reasonable to ask what you are watching for.
Benign skin growths rarely turn malignant, but require timely removal if they do. In addition, it
is important to distinguish the benign growths described in this POD from malignant skin
tumors, such as squamous cell carcinoma or malignant melanoma.
Signs of malignancy include rapid growth or any sudden change in color or character. Growths
that bleed easily, ulcerate, or become suddenly itchy or painful may also be turning malignant,
although these can be signs of infection or irritation as well.
So, if you see any sudden changes that cause a worry, contact your vet. He or she can remove the
lump and send it to the lab for histopathology. That’s the best way to set your mind at ease.
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GLOSSARY FOR COMMON SKIN GROWTHS
Apocrine Sweat Gland
The most abundant type of sweat gland in domestic animals; found
in haired skin and specialized regions such as the anal sacs. These
glands produce sweat under nervous-system control, and the sweat
contributes to a protective film on the skin. Specialized apocrine
sweat glands are located in the external ear canal and eyelids.
Benign
A cancer having slow growth and/or a generally good prognosis
Congenital
Existing at birth
Conjunctiva
The delicate membrane lining the eyelids and covering the edges of
the eyeballs (ie, whites of the eyes)
Corticosteroid
A drug that mimics the hormones involved with controlling
inflammation and swelling; these are sometimes referred to as
steroids, but they should not be confused with the anabolic steroids
used in muscle/body building.
Elizabethan Collar
A cone-like apparatus fitted to the neck of animals to physically
prevent them from licking or chewing an affected area
Epithelial Cells
The cells covering the internal and external surfaces of the body,
including the lining of vessels and other small cavities
Histiocyte
A large phagocytic cell of the immune system. Histiocytes and other
macrophages gobble up invading organisms and either destroy them
or process them for destruction by other immune cells.
Histopathology
The laboratory discipline in which tissues (eg, biopsy samples) are
examined under a microscope to determine how the tissue has
changed with disease.
Imiquimod
A topical drug with antiviral and anticancer properties. This drug
stimulates the immune response locally and is used in veterinary
medicine to treat viral papillomas and some malignant skin cancers.
Interferon
A natural cytokine released by cells when invaded by viruses.
Interferon is not itself an antiviral agent but rather acts as a
stimulant to noninfected cells, causing them to produce another
protein with antiviral characteristics, thereby protecting other cells
from infection.
Keratinocytes
The cells of the epidermis that synthesize keratin, which is the
protein-rich material that makes up the stratum corneum, hair, and
nails
36
GLOSSARY COMMON SKIN GROWTHS
Local Anesthetic
An agent injected into the local area, often under the skin, to deaden
the feeling to that area so that surgery can be performed on a
conscious patient
Malignant Melanoma
A cancerous, mole-like tumor containing dark pigment granules
called melanin
Pedunculated
Having a peduncle or stalk at the base
Plaque
A patch or flat area as opposed to a discrete lump
Polyp
A small mass that can be attached to the surface by a thin stalk of
tissue. Polyps are pedunculated.
Purulent
Containing or forming pus
Retinoid Drugs
Any of a number of drugs derived from vitamin A (retinal) that are
used to treat skin conditions such as acne and psoriasis
Squamous Cell Carcinoma
A relatively common malignant tumor of dogs and cats, which
occurs most commonly on the face and ears of white cats
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common skin growths

Transcription

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