CANCER….TOO CLOSE TO HOME!
Quinn, a very good friend of mine (and fellow EG writer) recently informed me
that her beloved 10 year golden retriever, U-CH, U-UD, OTCH Aero-Jett’s Wide
Retriever UDX JH WC OBHF, Can CD, fondly called by his many friends and admirers
as “CATCH”…. had a suspicious looking growth on his leg.
She quickly made an appointment and got him in to see his vet. The growth
was removed, he was sent home with 6 staples in his leg and a tissue sample was
sent off for a biopsy. We all waited
for the results, hoping and praying the pathology report would come back
“negative”. Unfortunately, on
April 23rd we learned the growth was a Grade 2 Mast Cell Tumor.
She will be taking her boy to the
course since I consider her “boy” one of mine, I immediately started
researching the disease to see what she and the “CatchMAN” and all of us
that love him dearly might be up against!
Below is an article I found on Mast Cell Tumors.
It is authored by KATE CONNICK. It
gives a general overview of what a Mast Cell Tumor is, the causes, the
treatments, the prognosis and includes other general information.
This article, along with others authored by Kate Connick can be found at:
MAST CELL TUMORS (MCT)
cell tumors (MCT) are cancerous proliferations of mast cells. Although
they can and will spread throughout the body, the danger from mast cell tumors
arises from the secondary damage caused by the release of chemicals that they
produce. These chemicals can cause systemic problems that include gastric
ulcers, internal bleeding, and a range of allergic manifestations. Clearly, mast
cell tumors affect both lifespan and quality of life. Sometimes mast cell tumors
are referred to as "the great imposters," as there is no way to
definitively identify them without a biopsy and pathology report. Mast cell
tumors vary widely in their size, shape, appearance, texture, and location. It
can be difficult not only to recognize mast cell tumors but to predict their
course. They may be relatively innocent or aggressively malignant. As mast cell
tumors are very common in dogs, it is important for the regular pet owner to
have at least a basic understanding of what they are and how they work.
cells are specialized cells that normally are found distributed
throughout the body and help an animal respond to inflammation and allergies.
Mast cells can release several biologically active chemicals when stimulated,
among them histamine, heparin, seratonin, prostaglandins and proteolytic
enzymes. Although these chemicals are vital to normal bodily function,
especially immune response, they can be very damaging to the body when released
in chronic excess.
names: Histiocytic mastocytoma, mast cell sarcoma, mastocystosis
(when there is systemic involvement).
Mast cell tumors are among the most common tumors in dogs and are the most
common type of skin cancer found in dogs. Approximately 1/3 of all tumors in
dogs are skin tumors, and up to 20% of those are mast cell tumors. The most
common location to find mast cell tumors is, by far, the skin, followed by the
spleen, liver, and bone marrow. Approximately half of all cutaneous (skin)
MCT’s are found on the body proper, another 40% on the extremities (most
frequently the hind limbs), and the remainder on the head or neck. Approximately
11% occur in more than one location.
No one fully understands what causes cancer. Mast cell tumors are very common in
dogs, yet they occur far less frequently in cats and very rarely in human
beings. They occur in dogs of all breeds, ages, and genders and can occur
anywhere on the body. There appears to be a genetic component, as certain breeds
are predisposed to developing MCT. Among the most common victims are beagles,
Because the cause is unknown, there is no known way to prevent mast cell cancer.
Presumably, the best one can do is to maintain their pet’s overall health and
be alert to signs of tumor growth or ill health.
hopefully begins early when the alert pet-owner notices a growth on his dog. The
vet may take a fine-needle aspirate from the growth to submit a sample for
preliminary biopsy. The entire tumor will then need to be fully removed, if
possible, and submitted for biopsy. Blood tests may include a complete blood
count, serum chemistry profile, and buffy coat. The CBC may reflect low or high
white blood cell count, low platelet count, elevated mast cell counts. The buffy
coat is diagnostic (although subject to false-positives) and reflects mast cells
circulating in the bloodstream where they are ordinarily not found in large
numbers. A positive buffy coat suggests bone marrow involvement. Other tests may
include urinalysis, lymph node aspirate, bone marrow aspirate, x-rays, and
ultrasound. The pathologist assigns a "grade" to the tumor, a somewhat
subjective assessment of how well differentiated the cells are and therefore how
aggressively malignant the cancer appears to be. The practicing veterinarian
and/or oncologist assigns a "stage" to the cancer, as well. The
supplemental lab work gives an estimate of how great a foothold the cancer has,
and this is reflected in the staging.
Grade: The pathologist will apply specialized stains to the tumor
sample and microscopically examine it in order to determine its grade. AgNOR
staining appears to be the most conclusive prognosticator for mast cell tumors.
Tumor grade is associated with the degree of differentiation of the mast cells.
The majority of MCT are Grade 1 tumors and are well differentiated and appear to
have a very good prognosis with no treatment beyond complete surgical removal.
Grade 2 tumors are moderately differentiated, and the prognosis and treatment
options are perhaps most complicated and difficult to predict. Grade 3 tumors
are poorly differentiated, very aggressive, and most likely to rapidly
metastasize. They carry the poorest prognosis but are fortunately the least
common. Histiologic grade is most predictive of prognosis.
Staging refers to degree to which the cancer has already spread at the time of
diagnosis. Tumors caught early - before they have invaded other tissues or
caused signs of systemic disease - logically carry the most optimistic
prognosis. MCT most commonly metastasizes to lymph nodes, bone marrow, liver and
spleen, so much of the lab work focuses on these areas to detect and assess
abnormalities. It is unusual for MCT to spread to the lungs, as is so common
with many cancers. In simplest terms, Stage 1 refers to a single tumor with
clean margins and no signs of spreading. Stage 2 and Stage 3 show progressively
greater signs of invasion, perhaps to local lymph nodes, demonstrating dirty
margins, or presenting as multiple tumors. Stage 4 involves systemic metastasis
and carries a grave prognosis.
symptoms: The most obvious sign of mast cell cancer is likely to be a
tumor of some sort. Mast cell tumors can appear singly, in groups, lie on the
surface of the skin or underneath it, crop up anywhere on the body, and defy
easy description. You just don’t know it’s a MCT by looking at it. Most (at
least half of) mast cell tumors are found in or under the skin on the trunk of
the body itself, and the vast majority of the remainder are found on the
extremities, especially the hind limbs. They are less commonly found on the head
and neck, and less commonly still arise from tissues other than the skin. If
they are very swollen or ulcerated, there may be pain, but most MCT’s are
unlikely to be painful. It has been observed that higher-grade tumors may be
more likely to be ulcerated in appearance and cause local irritation.
characteristic quirk of mast cell tumors is the tendency for them to change in
size, even on a daily basis. A tumor that gets bigger and smaller, seemingly on
a whim, may be a MCT. Another idiosyncrasy is the potential of the tumor to
produce "Darier’s sign" if poked and prodded. Handling these tumors
- even a routine veterinary palpation or needle aspirate - can cause a heavy
release of histamine that results in swelling, redness, itchiness, hives (wheal
symptoms: Symptoms are variable, depending on the location of the
tumor and the degree to which is has developed and/or spread. Signs of systemic
involvement may include: loss of appetite, vomiting, bloody vomit, diarrhea,
abdominal pain, dark or black feces, itchiness, lethargy, anorexia, irregular
heart rhythm and blood pressure, coughing, labored breathing, various bleeding
disorders, delayed wound healing, enlarged lymph nodes.
for mast cell tumors almost always first involves surgically removing the entire
tumor, if that is possible. It is particularly important to remove a wide margin
or large area of healthy tissue (2-3 cm in each direction) around the perimeter
of the tumor. The idea is to capture any stray cancerous cells that aren’t
immediately obvious. In some areas, such as a leg or paw, it is virtually
impossible to remove sufficient tissue to satisfy this 2-3 cm oncological rule.
The tumor is then submitted to a laboratory for biopsy, and a pathology report
is generated. Very important is the determination of whether or not the margins
of the submitted tissue removal are clean (showing no signs of cancerous cells)
or dirty (showing invasion of cancerous cells). If the margins are dirty,
further surgery or radiation may be indicated to attempt to remove or kill any
remaining cancerous cells. Nonetheless, a significant proportion of tumors that
are incompletely excised (i.e., dirty margins) do not return.
complete surgical excision, treatment options depend on factors that suggest the
aggressiveness and status of the cancer. Low-grade tumors are generally treated
locally with surgery, with or without radiation. High-grade tumors may be
treated systemically with prednisone and/or other chemotherapy. Sometimes the
only "treatment" is supportive care intended not to extend the dog’s
life but to make what remains of it as comfortable as possible.
treatments: Surgery is used to remove local cancerous tissue when
possible. Sometimes surgical sites for MCTs are resistant to healing. Radiation
may be used afterwards to locally kill off remaining cancerous cells. Sometimes
radiation is used in place of surgery to shrink tumors that cannot be easily
operated on. Radiation is highly effective in controlling mast cell cancer, yet
radiation is not for everyone. Dogs treated for mast cell tumors may have 3-5
radiation sessions per week for 3-5 weeks and must be anesthetized for each
treatment. This may cost several thousand dollars, may require travel and/or
boarding during the treatment period, and may have short or long-term side
effects that owners find objectionable.
treatments: Prednisone (a corticosteroid) appears to be the drug of
choice in treating mast cell cancer, so much so that many veterinarians will
routinely prescribe several weeks or months of prednisone subsequent to surgical
removal of any mast cell tumor. In the great scheme of things, prednisone is
inexpensive and safe. Side effects include increased drinking, urination, and
appetite and potential gastrointestinal upset. If a tumor has a reasonably high
metastatic potential, or if it has already metastasized, prednisone is likely to
other chemotheraputic drugs are used in combination with prednisone if the mast
cell cancer appears to have metastasized. These may include: CCNU (lomustine),
vinblastine, vincristine, doxorubicin, mitoxantrone, cyclophosphamide (cytoxan),
and L-asparginase. These are all heavy-duty drugs with potential side-effects
that include severe immunosuppression, vomiting, diarrhea, liver damage. Several
studies seem to demonstrate their limited efficacy in conjunction with surgery,
but in and of itself, chemotherapy is no match for inoperable or metastatic mast
cell cancer. Responses to chemotherapy are minimal in cases of MCT.
treatment (supportive care): Sometimes one cannot do anything
more than offer supportive care to a dog with mast cell cancer. The cancer may
have spread too far. The dog may be old or have other health impairments. The
owners may object to more aggressive treatment. It is the inability to manage
such things as vomiting/diarrhea from gastric ulceration that typically marks
the end of quality of life for the dog with mast cell cancer. Thus, controlling
symptoms may be more important than battling the cancer, per se.
drugs are used to prevent or manage potential problems caused by the chemicals
that mast cells release. In effect, one isn’t addressing the cancer itself.
One is simply trying to maintain quality of life by fighting the deleterious
effects of the chemicals secreted by the mast cells. Corticosteroids like
prednisone, antihistamines like benadryl, and antacids like tagamet, zantac or
pepcid are often used as a matter of course after surgery and/or radiation and
are routinely used to maintain comfort in dogs where the cancer cannot otherwise
be treated or has spread. Sucralfate may be helpful with dogs that have bleeding
ulcers, as it coats the surface of the ulcer to protect it and allow for
healing. Further, there are now special foods available for dogs with cancer -
like Hills Prescription Diet n/d - which are intended to preferentially nourish
the patient but not the cancer itself, thereby increasing both quality and
length of life.
Dogs who have had mast cell tumors are more likely to develop more mast cell
tumors. 50% of surgically removed mast cell tumors will re-grow in the same
Prognosis is highly variable and dependent on many factors including tumor
location, histiologic grade and clinical stage. One statistic suggests that
approximately half of all MCT’s are curable with complete surgical removal and
prednisone treatment. Dogs that are tumor-free after 6 months are considered
unlikely to have a recurrence. Primary tumors that originate in areas other than
the skin tend to be more aggressive than cutaneous tumors. MCT in preputial
(sheath), perineal (groin), subungual (nail bed), and oral regions areas are
generally the most malignant. MCT of bone marrow or visceral tissue is
particularly grave. The higher the grade or stage, the worse the prognosis.
Boxers are especially at risk for developing mast cell tumors, yet they tend to
have less aggressive (lower grade) MCT than other breeds. Dogs showing systemic
signs and dogs whose tumors return after surgical removal have poorer prognosis.
Similarly, the faster the growth of the tumor, the worse the prognosis. One
study found that dogs with tumors that grow more than 1cm per week have only a
25% chance of surviving 30 weeks. MCT's that exist locally for several months
without showing signs of rapid growth tend to be benign.
MCT: A grade 1, stage 1 cutaneous MCT is likely to never return
after surgical removal. The estimated long-term survival rate for dogs with such
tumors is over 90%.
MCT: It is reported that 50-75% of dogs with Grade 2 MCT survive
long-term (beyond 35 weeks). Another study concluded that 44% of dogs with Grade
2 MCT survived long-term (over 4 years) after nothing more than complete
surgical removal of their tumors. Yet another author reports a 45% mortality
with radiation: Radiation may increase survival. One study concluded
that 86% of its subjects, dogs with Grade 2 MCT, survived long-term (over 5
years) with a combination of surgery and radiation (compare that to the 44%
mentioned in the previous paragraph). Another author cited a 48-77% remission
rate for treatment plans that included radiation. Yet another study reported a
94% disease-free rate at one year in dogs with Grade 2 MCT (dirty margins) after
surgery and radiation, and an 86% disease-free rate after 5 years. And another
study still reflects a 75% survival rate two years after radiation and
prednisone treatment. As with anything, any research results need to be taken
with a grain of salt unless the entire research protocol is examined. These are
merely statistics that one can readily discover in various citations online and
in books. Nonetheless, they all appear to suggest that radiation after complete
surgical removal is statistically the most effective way to combat (primarily
Grade 2) MCT.
with prednisone: Prednisone, with or without other chemotherapy, is
estimated to induce partial or complete remission in approximately 20% of canine
patients with MCT. The reason for prednisone’s effectiveness is not fully
understood, yet its use is pervasive in treating this condition.
MCT or metastasis: Only 15% of dogs with Grade 3 MCT will be alive 7
months after surgery, and only 6% will be alive after 2 years. Once mast cell
cancer has metastasized, dogs tend to die within 6 months as the symptoms of
systemic illness (e.g., gastric ulcers) can no longer be managed and the animal
loses its quality of life.
line: Mast cell tumors occur frequently in dogs. They are well
documented and well understood in some respects, yet they are unpredictable in
appearance and behavior. No one knows what causes mast cell cancer, nor how to
cure it with certainty once it has metastasized. The best one can do as a pet
owner is be attentive to the general health of one’s dog and get all unusual
lumps and bumps examined carefully to rule out MCT or to catch it in the
earliest stages. MCT can be lethal, but it is not necessarily so. If you’d
like to send me the details of your experience with mast cell cancer in your
dog, I’d be fascinated to read it. Perhaps I can compile a section with this
information at some point in the future.
Disclaimer: I am not a veterinarian, nor do I
have any particular veterinary/scientific/medical training or knowledge. I
don’t even play a vet on tv. This article represents my understanding, as a
layperson, and is intended merely as a starting point for the fellow
layperson/pet-owner. I assume no responsibility for inaccuracies. As always,
consult with a qualified veterinary professional to assess and manage your
pet’s health. Please notify me if you encounter factual errors or would like
to further my understanding of the above condition. Kate Connick
At the time that I was initially putting this article together for EverythingGolden and prior to submission, Pat was scheduled to take Catch to the
next time, remember:
h o r n s may
hurt you, men desert you, sunlight turn to fog; but you're never
friendless ever, if you have a dog."--Douglas Mallock—
As always, comments welcome!
Mary Lou Gerace
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