I am confident that the term your veterinarian used is "mast cell
tumor." This kind of tumor can also be called a "mastocytoma."
A mast cell is an immune cell that helps the body to detect foreign
substances in tissues, and assists in the immune response to those
substances. A mast cell tumor may be either benign or malignant. In
cats, such tumors are most commonly benign. Mast cell tumors can be
excised surgically by your veterinarian. If the tumor is determined to
be malignant, additional drug and/or radiation therapy may be
necessary.
Several years ago my 10-year-old cat, Seymour, underwent several
surgeries for mast cell tumors on his ear and face. At that time I did
some research so that I would have a better understanding of what was
going on. I am sharing that information, and I have gathered
additional material that will help give you an overview of this type
of tumor. Your cat's prognosis, of course, will depend upon a
definitive diagnosis, but this material will help you to understand
more about mast cell tumors in general.
===================================================
Mast Cell Tumors in Dogs and Cats
Very few tumors present in such a wide variety of clinical signs: they
are indeed the great impostors! They can look like anything and behave
differently depending on the histologic type, location and the extent
of the disease. The following is a brief discussion about these
tumors...
Mast cell tumors may exist in cutaneous or extracutaneous locations.
The most common sites in the dog for mast cell tumors are the skin of
the trunk and perineal region (50%) and the skin of the extremities
(40%). The remaining 10% arise from cutaneous sites of the head and
neck. Mast cell tumors are reported to arise in multiple cutaneous
locations in approximately 11% of the cases. The majority of mast cell
tumors are found in the head and neck region in the cat. Occasionally,
the mast cell tumors are located strictly in the spleen of cats...
Diagnostic workup of mast cells usually includes a number of
procedures. These include a complete blood cell count (CBC), serum
chemistry profile, and urinalysis... A CBC is valuable in assessing
animals with mast cell tumors because those animal patients with
systemic mastocytosis occasionally have peripheral cosinophilia and
basophilic in addition to circulating mast cells. Mastocytemia is a
more common clinical phenomenon in the cat than in the dog...
Peripheral mast cell counts may be high in cats with mastocytosis and
have accounted for up to 25% of the total white cell count...
Abdominal radiographs may be useful in evaluating dogs and cats. This
is especially true in cats because of the high incidence of splenic
involvement in this species with mast cell tumors.
THERAPY
...Approximately 50% of the mast cell tumors recur at the surgical
site traditionally. Histologic grade is an important factor in
predicting recurrence at the surgical site. Those that are
undifferentiated tend to have a higher recurrence rate.
Cats with mast cell tumors with splenic involvement often will benefit
from splenectomy. Survival times of 10 weeks to 30 months have been
reported following splenectomy, even in patients with evidence of
syteinic mastocytosis.
Glucocorticoid therapy frequently results in partial or occasionally
complete remissions in canine mast cell tumors. However, cats appear
to be less responsive to glucocorticoid treatment...
Radiotherapy has been used alone or in combination with other
treatment modalities. Most reports indicate remission rates of 48 to
77%... The use of radiotherapy is somewhat expensive and is confined
to referral centers...
PROGNOSIS
...In general, cutaneous mast cell tumors carry a more guarded
prognosis in the dog than in cat. Mast cell tumors in the boxer arc
usually of a lower histologic grade than when found in other breeds.
Mast cell tumors in Siamese are of the less malignant histiocytic
type. Histologic grade has been shown to correlate with survival
following surgical excision by at least two investigators... In the
cat, in addition to the histologic grading system described for the
dog, the histiocytic mast cell variant tends to carry a better
prognosis than the traditional mast cell. Tumor location is considered
by many investigators to be an important prognostic feature. Tumors
located in the perineal or, preputial area are likely to metastasize
both locally and to deep lymph nodes.
Columbia Animal Hospital
http://www.cah.com/library/mstcll.html
===================================================
In the cat, tumors of the skin and subcutaneous tissue are second in
frequency only to tumors of the lymphoid system and account for
approximately one quarter of all tumors in the species... MCTs [mast
cell tumors] represent the second most commonly encountered cutaneous
tumor in the cat, accounting for approximately 20% of cutaneous tumors
in this species in the United States. The incidence of MCTs in cats
appears to have increased dramaticaly since 1950. MCTs in the United
Kingdom appear to occur much less frequently, accounting for only 8%
of all cutaneous tumors. Two distinct forms of cutaneous MCTs in the
cat have been reported: (1) the more typical mastocytic MCTs,
histologically similar to MCTs in dogs, and (2) the less common
histiocytic MCTs, with morphologic features characteristic of
histiocytic mast cells. An overall mean age of 8 to 9 years is
reported for cats with MCTs; however, the mastocytic and histiocytic
forms occur at mean ages of 10 and 2.4 years, respectively. Siamese
cats appear to be predisposed to development of MCTs of both
histologic types. The distinct histiocytic form of MCTs in cats has
been reported to occur primarily in young (< 4 years of age) Siamese
cats, including two related litters. In contrast to these reports,
Siamese cats have not been found any more likely to develop the
histiocytic form of MCTs than the mastocytic form, as reported in
another series of cases. This report found only two of seven cases of
histiocytic MCTs were from Siamese in their hospital population.
Earlier studies reported a male predilection for development of MCTS;
however, larger more recent series have failed to confirm such a
predilection.
Visceral MCTs appear to be more common in the cat than in the dog,
with up to 50% of MCT cases occurring in visceral sites in some
series. A splenic form (sometimes referred to as lymphoreticular MCT)
represents the most common differential for "splenic disease" in cats,
accounting for 15% of submissions in a series of 455 pathologic
specimens. The mean age of affected cats is approximately 10 years and
no breed or sex predilection is known. Intestinal MCT is the third
most common primary intestinal tumor in cats after lymphoma and
adenocarcinoma. 5 No breed or sex predilection is known. Older cats
appear to be at risk, with a mean age of 13 years; however, cats as
young as 3 years have been reported.
Max's House
http://maxshouse.com/tumors_of_the_skin.htm#Mast%20Cell%20Tumors
===================================================
The following four types of tumor comprise about 75% of all skin
tumors in cats: basal cell tumor, mast cell tumor, squamous cell
carcinoma, and fibrosarcoma. The head, including the ears, is the most
common site for basal cell tumor, mast cell tumor and squamous cell
carcinoma. For all four types of tumor, peak number of cases occurs in
cats older than 10 years. Sex predilection for the common skin tumors
is not apparent... Mast cell tumor can form solitary or multiple
dermal or subcutaneous nodules. Alternately, the tumor may appear as
erythematous plaques. Feline mast cell tumors are usually benign,
although anaplastic variants may recur or metastasize. Mast cell tumor
occurs in cats of all ages, including kittens. The tumor in kittens
may regress spontaneously. About 2/3 of mast cell tumors occur on the
head, particularly at the base of the ears or forehead. Siamese cats
are predisposed to mast cell tumor. A less common variant of mast cell
tumor with a "histiocytic" appearance occurs in younger cats.
Charles Louis Davis, D.V.M. Foundation
http://www.afip.org/CLDavis/syllabi/skintum.txt
===================================================
Cats: Prognosis of mast cell tumors of the skin is usually excellent
and surgery is generally curative. Prognosis of mast cell tumors
localized to the spleen is good and many live for an additional one to
two years after the spleen is removed. Prognosis is somewhat guarded
if the mast cell tumor is located in the gastrointestinal tract.
Vet Surgery Central
http://www.vetsurgerycentral.com/mct.htm
===================================================
Mast cells are a part of the body’s normal immune system. They help to
coordinate a response to foreign substances that invade through the
skin. Mast cell tumors occur in two forms: cutaneous and visceral. The
mean age of affected cats is 10 years old. Siamese cats are
predisposed to mast cell tumors. The cause of mast cell tumors is
unknown.
Mast cell tumors produce histamine, heparin, and other vasoactive
compounds. Complications of these tumors are associated with
widespread degranulation of mast cells. These include coagulation
disorders, GI ulcers, anaphylactic reactions, altered smooth muscle
tone, hypotensive shock, and labored breathing.
The most common sites of metastasis are: liver (90%), visceral lymph
nodes (73%), bone marrow (40%), lung (20%), and intestines (17%).
Typical presenting signs of systemic illness include: depression,
anorexia, weight loss, and intermittent vomiting. The treatment of
choice for mast cell tumors is surgical resection.
College of Veterinary Medicine, the University of Minnesota
http://160.94.9.156/ahc_content/colleges/vetmed/
===================================================
"My 5 year old, neutered male [cat], Patrick, had a growth removed
from his right cheek (in the whisker area) by the vet this past
Monday. The removed tumor was biopsied and the lab report said that it
was a mast cell tumor and revealed a "low grade malignancy". My vet
said that the grade was only one notch above the benign category. Her
recommendation was to go back and surgically remove a wider and deeper
area of tissue at the site where the tumor was removed from. Plus to
remove the tissue at a site below his chin that has to this point
thought to be a pimple/blackhead(?), just to be sure. Patrick's in
surgery today. The vet also says that there will probably more tumors
in the future and to just have them removed as they pop up. What is
your opinion overall? Other questions are: Does this type of tumor
mean that my cat has "cancer", meaning prolonged illness? If all of
the "bad" tissue, plus the surrounding area is removed, what are his
chances for a complete cure? Does this type of cancer stay fairly
localized? I don't think my vet knows if it's spread (metastasized) or
not. What are the chances that it has spread/ will spread? What
treatments other than surgery are recommended?"
In cats, most mast cell tumors found in the skin are benign. In dogs,
mast cell tumor malignancy is more common. The cause of mast cell
tumors is unknown. The types of treatments range from simple excision,
to cryosurgery, electrosurgery, chemotherapy, radiotherapy and or
immunotherapy. In dogs, systemic complications of mastiocytosis are
seen more frequently, and thus the treatments are more aggressive. For
a cat with a growth like you describe for Patrick, what you say your
vet is doing sounds very appropriate. If more growths crop up, they
should be similarly removed. The likelihood of this happening, or of
metastases from the original tumor seeding further growths is not
possible for me to predict. One literature source I have says new
tumors are found later about 1/3 of the time. The bottom line is that
cutaneous mast cell tumors in cats are not usually considered highly
malignant or metastatic.
The Internet Vet Column
http://www.io.com/~tittle/ivc/1994/internet-vet.1.08.html
===================================================
Mast Cell Tumor
Q: My cat had a bump behind her ear that eventually grew, and my vet
removed it. I just got the biopsy results back, and it was a mass cell
tumor. He told me that in dogs, there are levels to classify the
severity of tumors, but there are no levels for cats. I never really
got a clear answer of whether or not it is malignant, and I'm to talk
to him again about treatment. He said he was concerned because of how
extensive the tumor was. Do you have any additional information on
mass cell tumors in cats? What is the survival rate, and can they be
treated?
A: Holly- Most mast cell tumors in cats are solitary benign tumors but
they can be malignant. In most cases simply removing the tumor is
sufficient. If your vet is worried, it may be worth consulting with an
oncologist to see if something like postoperative radiation therapy or
chemotherapy may be helpful. The oncologists tend to have the most
recent information on success rates, etc. when it comes to tumors and
tumor treatments.
Mike Richards, DVM
VetInfo
http://www.vetinfo.com/cmastcell.html#Mast%20Cell
===================================================
Mast cell tumors in the skin of cats usually are benign and can be
managed effectively by simple surgical excision. Some mast cell tumors
in young Siamese cats may even spontaneously regress in time without
any treatment...
Treatment for mast cell tumors may include one or more of the
following:
Wide surgical excision (removal) of a well-differentiated mast cell
tumor of the skin
Radiation therapy for local control of a less well-differentiated skin
tumor
Chemotherapy in selected cases
...No method of protection against development of mast cell tumors can
be recommended because the cause of these tumors is unknown. Careful
monitoring of your pet is important, especially if you have one of the
breeds known to be at increased risk. If you notice a lump in your
pet’s skin, the mass should be examined by a veterinarian as soon as
possible.
PetPlace
http://petplace.netscape.com/articles/artShow.asp?artID=689
===================================================
Mast cells are an odd cell. They originate in the same cell lines as
white blood cells but spend their life in the connective tissues which
support all of the body's organs, making them very widespread in the
body tissues... These cells are one of the first lines of defense
against foreign invaders and are therefore more common in tissues
susceptible to attack, such as the ocular tissues and the digestive
tract... When cancer occurs in these cells it may be referred to as a
mast cell tumor or as a mastocytoma...
There are some controversies in treatment options for mast cell
tumors. Whether or not to pursue local radiation therapy at the site
of the tumor removal is one area in which the best answer is not
always clear. With a 90% success rate for surgical removal alone for
Grade I tumors, it is hard to figure out whether or not to pursue
radiation therapy, for instance. For Grade II tumors, radiation
therapy increases the long term survival rate from about 45% to about
85%, so it is more clearly beneficial in this case...
Prednisone was reported to be a chemotherapeutic for mast cell tumors
in one study but this has not been as successful in follow-up studies.
At the present time prednisone is considered to be helpful in
extending the time between surgical removal of mast cell tumors and
recurrence of the tumors in about 20% of patients.
VetInfo
http://www.vetinfo.com/0800example.html
===================================================
Search terms used:
"mast cell tumor(s)" + "cat"
"feline mast cell tumor(s)"
"mastocytoma(s)" + "cat"
"feline mastocytoma(s)"
===================================================
I hope this gives you some insight into the term "mast cell tumor." As
one who is "owned" by several kitties, I sincerely hope your cat will
recover soon. If you have any questions about my research, or if a
link does not function, please request clarification and allow me to
offer further assistance before you rate my answer.
Best wishes,
pinkfreud |
