To Cheryl Cato:
 
>How lucky we are to have you on this list!  Thanks so much for the info for my
>new vet - and the offer to allow her to call you.  She appreciated it - and I
>know I sure do!  I cut all the postings by you out of the articles I have saved
>from this list and gave them to her as well.  Her response:  "Wow - I need to
>get a PC!"  Absolutely!  Thanks again.
 
   Wow!  Thanks for the glowing praise.  That's the nicest thing I've heard in a
while.....but you'll give me a swelled head.
 
Here's something else for your vet (and tell her to get that PC - with all of
the medical information available out there fro veterinarians, I'm always amazed
that they are yet an integral part of every vet's arsenal....
 
        The result is the result of another day off from work (the 15th winter
storm of the season hit Washington D.C. yesterday....
 
 
The following article may be reprinted by anyone desiring to disseminate this
information in a newsletter or non-commercial publication.  This material may
not be altered or changed in any way.  Under Title 17 of the U.S. Code, Section
105, copyright protection is not available for any work of the United States
Government.
 
 
        SKIN TUMORS IN THE FERRET
 
        In previous articles, we have discussed the two most common neoplasms of
the ferret, islet cell tumors and adrenal tumors.  Now lets look at the third
most common group, the various tumors of the skin.
 
        Ferret skin tumors are very common, and increase in frequency with age.
Let's get one point straight right away - the VAST majority of skin tumors in
ferrets are benign.  Malignant tumors, or tumors that will grow rapidly, invade
and destroy adjacent tissues, and metastasize to distant sites where they can
continue their destructive processes, are very rare in ferret skin.
 
        The most common skin tumor in ferrets, both at the AFIP and in a recent
retrospective study by Parker et al (Veterinary Pathology, Jan 1994) is a tumor
composed of undifferentiated epithelial cells, known as a basal cell tumor.
This cell has the ability to differentiate into several different components of
normal skin, including glands (at which time it is called a sebaceous
epithelioma), hair follicles, or just simple sheets of epidermal cells.  Most
tumors show at least two, if not more of these structures, a feature which has
caused some pathologists in the past to consider them malignant; however, now we
know that this is not the case.
 
        Basal tumors appear as small warty growths that may have a depressed
centers.  They grow slowly, and are freely movable, as they do not involve
structures underneath the skin.  They are easily removed, and do not recur
(unless the surgeon fails to remove all of the tumor at the time of surgery.
They are most common on ferrets over the age of four.  While they should be
removed, as they may become traumatized and infected, owners should be reassured
by the good outlook (or prognosis) with which they are associated.
 
        The second most common skin tumor in the ferret is the mast cell tumor.
Mast cells are a population of cells in the skin which are closely associated
with blood cells.  Normally, they mediate allergic reactions, liberating certain
chemicals which cause vascular dilation, causing the redness associated with
hives and other allergic conditions.  Mast cell tumors, although they are
associated with a high rate of malignancy in the dog and cat, are generally
benign in the ferret.  There are no reports of malignant mast cell tumors in the
ferret medical literature.
 
        Mast cell tumors usually appear as flat, often hairless, small plaques
on the ferret's body.  They are also freely movable and do not involve
underlying structures.  They may be somewhat crusty, as ferrets will often chew
or scratch at these sites, as some of these tumors itch.  In rare cases, animals
may have multiple mast cell tumors at once.  Excision of these tumors is
considered curative.
 
        Another very common skin tumor is not actually a tumor, but a cyst, or a
dilated sweat gland, known as an apocrine cyst.  Apocrine glands may also form
benign, or rarely, malignant tumors, but by far, the most common lesion
associated with these glands is a simple cyst.  These cysts appear as small,
round, hard "bubbles" just underneath the skin surface.  If squeezed, they may
rupture and spill their contents into the surrounding tissue.  This causes a
marked inflammatory response and gives the appearance of rapid growth.  Once
again, surgical excision is curative.  These cysts may occur anywhere on the
body, but the prepuce, or penile sheath of males, is the most common site, in my
experience.  There is a higher concentration of apocrine glands here that at
anywhere else in the ferrets skin, so, logically, there would be an increased
incidence of cysts at this site as well.
 
        Well, then, where are the bad tumors?  There are actually very few of
them.  In the last three years, I have seen less than five.  All of these skin
tumors arose from those apocrine sweat glands that we just talked about.  This
malignant tumor, or carcinoma, generally grows rapidly, and in contrast to most
other skin tumors, often becomes firmly anchored to underlying muscle.  It
rapidly invades and destroys adjacent skin and may metastasize to the local
lymph nodes, or in the case of two the five cases, the lungs, resulting in the
death of the animal.  While excision may be curative if caught early, masses of
this type that have reached any size are associated with a much poorer outlook.
 
        Of course, malignant tumors arising internally, such as lymphosarcoma,
may metastasize to the skin, as they may metastasize to any other site.  I have
not discussed these neoplasms, as they are generally uncommon and do not
originate in the skin.
 
        One final note - while excision of the vast majority of the tumors that
we have discussed is curative, there is nothing to prevent a second basal cell
tumor, or mast cell tumor, from arising in another site at a later date.  This
does not worsen the prognosis for that animal, just requires a second trip to
the vet for removal. And remember, always have your vet get those tumors
analyzed - while most skin tumors are benign, you and your pet will sleep better
knowing about that tumor for sure.
 
Bruce Williams, DVM
 
 
References:
 
1.  Parker, GA et al.  Histopathogic features and post-surgical sequelae of 57
cutaneous neoplasms in ferrets (Mustela putorius furo).  Veterinary Pathology,
30(6) 499-504, 1993.
 
2.  Fox, JL.  Biology and Diseases of the Ferret.  Lea and Febiger,
Philadelphia, 1988.
 
[Posted in FML issue 0746]