Copyright © 2011 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Benign Skin Tumors in Dogs
Emily Rothstein, DVM, DACVD
Several types of benign skin tumors can develop from skin struc-
tures in the dog. Sebaceous adenomas are growths involving the
sebaceous glands (those glands that produce sebum or a waxy sub-
stance for the skin and coat) and the ducts. Sebaceous epitheliomas
are growths that develop from only a part of the gland, called basal
cells. Sebaceous gland nodular hyperplasia is a small bump that
occurs when the entire gland grows larger and pushes up through
the surface of the skin.
Another group of benign tumors, called hair follicle tumors,
can arise within the hair follicle or hair shaft.
It is not known why these normal skin structures develop into
benign skin tumors.
Sebaceous growths are common in older dogs, especially in the
cocker spaniel, Siberian husky, miniature poodle, black and tan
coonhound, beagle, and dachshund. Sebaceous tumors are uncom-
mon in the cat, but Persian cats may develop them more often than
others. These tumors can occur alone or in small groups, are often
yellow-pink in color, and are shaped like a cauliflower. They often
have a wart-like appearance. Adenomas are small to medium in
size (usually less than
⁄ 2 inch). Epitheliomas are often larger; they
may be fingerlike projections or flatlike adenomas. They vary in
size from quite small to inches across .
Nodular hyperplasia bumps can resemble sebaceous adenomas
or epitheliomas. They usually have a greasy scab on the surface
but rarely bother the pet unless they are located between the toes,
under the collar, or in some area where they can become irritated.
Sometimes, the waxy substance produced may be irritating if it
sits on the surface for a while. Some dogs develop dozens of these
bumps over their entire body.
Benign hair follicle tumors can range from less than 1 inch to
the size of a golf ball or an orange. They often are partially hairless,
and if one looks closely, a central depression can usually be seen
on the surface. Some of these lesions rupture, exuding gray-white,
thick material that may resemble pus but is really material from the
hair follicle. The tumors usually occur in middle- to older-aged pets.
Some commonly affected breeds are the German shepherd dog,
poodles, Kerry blue terrier, Old English sheepdog, and keeshond.
Removal and biopsy of the tumor allows the exact type to be iden-
tified but may not be recommended if the tumor is causing no
signs. An aspirate of the mass may be recommended to rule out
other skin tumors of similar appearance.
TREATMENT AND FOLLOW-UP
There may be no need to remove many of these tumors unless they
bother the pet or the owner, especially since they usually only cause
cosmetic problems. If the tumor bothers the pet, becomes irritated
and inflamed, ruptures, or bleeds often, removal may be recom-
mended. Removal may also be recommended for certain sebaceous
Usually, if the tumor is completely removed, no follow-up is
required. Most dogs continue to develop more of these tumors
throughout their adult lifetime.
The prognosis is good for most of these tumors, because they are
benign growths. In rare instances, the sebaceous epithelioma can
behave more aggressively and recur at the surgery site or spread
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