Mast cell tumors (MCTs) are fairly common tumors in dogs. They are most frequently based in the superficial layers of the skin, on any part of the body. Frequently, you will see ulceration over the part of the tumor, and the dog may scratch or bite in the affected region. The appearance of the tumor does not reveal its potential for spread or recurrence with any certainty. The tumors are often singular, but dogs may present with multiple nodules, or recurrent ones. Some nodules occasionally enlarge after which regress in size on their own, because of swelling within the tumor itself. Some nodules occasionally enlarge after which regress in size by themselves, because of swelling within the tumor itself. Some nodules occasionally enlarge and then regress in size on their own , due to swelling within the tumor itself. MCT look like just about anything, ranging from benign-appearing lumps (such as a lipoma), to more angry or ulcerated lumps, masses having a stalk or focal thickenings in the skin. MCT may change quickly in dimensions (become larger then smaller ) because of reactions round the mass. Some dogs might have signs of systemic disease, which can be caused by a few of the biologically active compounds throughout mast cells. In most cases, evidence of a MCT is definitely generated by examination of a fine-needle aspirate from the suspect mass, and aspiration is advised before elimination of full of to be sure it is not a MCT (or other skin malignancy), a finding that would demand a more aggressive surgery. MCT look like just about anything, which range from benign-appearing lumps (like a lipoma), to more angry or ulcerated lumps, masses with a stalk or focal thickenings in the skin. MCT look like just about anything, which range from benign-appearing lumps (such as a lipoma), to more angry or ulcerated lumps, masses having a stalk or focal thickenings in the skin. Often, obtaining blood for any complete blood count and biochemical profile, along with a urinalysis is going to be advised because these can help assess overall health and supply information that potentially influences treatment recommendations.

Mast cell tumors do not have a specific appearance. However, they’re fairly easily detected by a “needle aspirate and cytology.” Insertion of the small needle into the tumor (virtually painless) area is followed by examination of the cells under a microscope. Mast cells are large, round cells that usually have dark granules inside them. The granules contain substances which, when released, cause swelling, itching, and redness. Infrequently, when a large number of granules discharge their chemical contents to the bloodstream, vomiting, stomach ulcers, shock and even death may result.Mast cell tumors (MCT) in dogs are very common, accounting for approximately 20% of all skin tumors in dogs. For most dogs, the actual cause promoting the introduction of the tumor isn’t known. Mast cell tumors can arise from any skin site on the body, and may have a variety of appearances. Veterinary oncologists suggest that before any skin lump is removed, the cells in the mass be collected for examination to eliminate the lump like a mast cell (or another malignant) tumor. And mast cells are something that are easily identified on aspiration.

MCT Tumor Staging

Mast cell tumors could be somewhat unpredictable in their behavior, relative to other forms of tumors in dogs. Due to this, care is taken to “grade” the tumors which are discovered. The grade reflects their education that the malignant mast cells differ from normal, non-malignant mast cells. The stage can generally be correlated with tumor behavior, tumor recurrence, and survival of the patient. Mast cell tumors affecting the limbs, head, or neck tend to correlate having a more favorable prognosis than those found on the trunk or groin. Multiple mast cell tumors or those exhibiting rapid growth generally have a far more guarded prognosis. A pathologist determines the tissue grade from the tumor following the tumor is biopsied or removed.

*Grade I: well-differentiated-25% recurrence rate post-surgery

*Grade II: moderately differentiated-44% recurrence rate post-surgery

*Grade III: poorly differentiated-76% recurrence rate post-surgery

Treatment for mast cell tumors

Treatment for mast cell tumors may involve surgery (the mainstay), chemotherapy, and/or radiotherapy. Strategies for treatment provide the type and grade of the tumor, surgical feasibility, and the presence or absence of spread (dissemination) of malignant mast cells through the body. Your veterinarian will usually submit blood tests and ask for abdominal ultrasound or radiographs (x-rays) to determine the probability of malignant mast cells elsewhere in the dogs body. Bone marrow biopsies are no longer routinely done, because they haven’t proven to have high predictive value for tumor staging.Surgery is the mainstay of treatment of canine mast cell tumors. For their locally invasive behavior, wide margins of what appears to be normal tissue round the tumor needs to be removed to increase the chance the tumor has been completely removed. For mast cell tumors which were not, or due to location, couldn’t be completely removed, radiotherapy is often the very best strategy to residual disease, although a more aggressive second surgery can be done for some dogs. Chemotherapy may also be used to treat mast cell tumors, but chemotherapy is generally reserved for dogs with grade III tumors; mast cell tumors are notoriously unpredictable tumors with regards to reaction to chemotherapy. In addition to treatment of the tumors, some dogs is going to be treated with medications that tend to help fight the secondary effects of the tumor. These usually include drugs like prednisone, an anti-histamine like Benadryl, and an antacid type medication like Pepcid. The prognosis for completely removed grade I and grade II tumors is excellent. The prognosis for incompletely removed grade I and II tumors given radiation therapy after surgery can also be excellent with approximately 90-95% of dogs having no recurrence of tumor within 3 years of receiving radiation therapy. The prognosis for dogs with grade III tumors is considered guarded as local recurrence and/or spread is probably in most dogs. If your dog is diagnosed with a grade III Mast cell tumor most likely chemotherapy is going to be recommended as at least the main protocol. Drugs used at WSU include Lomustine and Vinblastine.

Surgery

For single mast cell tumors, a surgical procedure known as a “wide resection” is performed. This means aggressively excavating the tumor and surrounding tissues to ensure that a minimum of 3 cm of normal tissue in all directions is taken away. The margins of the removed tissue are examined by a pathologist to determine the presence associated with a lingering malignant cells. If negative, we refer to it as “clean margins”. When the pathologist suspects the presence of mast cells in the remaining tissues from the surgery site, we refer to it as “dirty margins”. An aggressive surgery early in the path of mast cell tumor disease is associated with the best overall prognosis. A grade I or II tumor that has been completely removed usually requires no other immediate therapy. A grade III tumor, multiple tumors, recurrent tumors, or tumors with dirty margins (those that for anatomical reasons couldn’t be subjected to further surgery) often require follow-up or “adjunct” therapy.

Radiotherapy

Radiation therapy is definitely an option for dogs whose mast cells tumors are localized, but too big for a clean resection or perhaps in a place difficult to resect for example tissues of the facial region, or as follow-up therapy for tumors with dirty margins. Dogs tolerate radiotherapy well, also it can offer long-term control for these tumors. Radiation therapy wouldn’t be right for dogs with multiple tumors or those with evidence of disease throughout the body since the radiation beam treats merely a single focus of disease.

Chemotherapy

Chemotherapy denotes the administration of certain anti-cancer drugs to be able to delay/prevent tumor growth or spread. It might be used before or after surgery, or alone.

Prednisone (a cortisone) is the most popular drug for therapy of mast cell tumors. It’s well tolerated by dogs and it is usually useful for no less than 6 months. If no new tumors appear within that time, your doctor may wean your pet from the prednisone completely. The side results of prednisone include putting on weight, increased appetite and thirst, bladder or skin infections, and panting. Occasionally, stomach irritation or ulcers may appear, or inflammation from the pancreas. Most of the time, the drug dose can be titrated towards the patient to minimize any overt symptoms. When the tumor type is decided to become aggressive, additional drugs for example stomach protectants may be prescribed to guard against untoward tumor effects.

For recurrent or multiple tumors, and for those tumors that cannot be surgically removed, combination chemotherapy can be effective in controlling tumor growth and spread for weeks to or more months. A cure by itself is generally not realistic, however, many dogs tolerate therapy extremely well. The 6-month protocol involves:

· Predinsone: high dose at first, then taper over 4 months

· Vinblastine: an outpatient injection, given once every A 3 week period

· Cytoxan ®: a dental chemotherapy drug, distributed by the owners on days 8, 9, 10, and 11 of a 21-day cycle.

Unwanted side effects

The side effects of prednisone are discussed above. Vinblastine and Cytoxan have the ability to cause nausea and or vomiting, though this isn’t usual. The most important possible side effects are decreasing the bodys defenses to ensure that frequent infections occurs, or (rarely) causing many mast cells release a their contents at the same time. Both situations could be life threatening. However, these are NOT common, and the risk of these is significantly lower than the chance of untreated mast cell disease. You’ll be given instructions on which to complete if any unwanted effects occur, so not hesitate to make contact with us.

Lomustine (CeeNu)

CeeNu is a potent oral chemotherapy drug that can be used once every three weeks in patients who MCTs have grown to be resistant against other treatments. It’s very well tolerated in general. However, because it can boost the risk of infection (especially seven days after it’s given), any noted fever, depression, weakness, or refusal to eat should be reported to us immediately. Infection is almost always completely reversible.

Prognosis

The factors which are known to influence patient outcome are grade of tumor (I is best, III is largest), completeness of surgical removal (clean margins), and tumor location. Dogs with high-grade tumors, multiple or recurrent tumors, or proof of spread towards the bloodstream or to other organs have a much more guarded prognosis for any lengthy survival.

Patient Monitoring

Close patient monitoring is essential in dogs with a good reputation for mast cell tumors. As with many tumors, early detection and treatment increases the chances of successful treatment. You may be asked to have your pet examined every 6-8 weeks following surgery, or every 21 days during chemotherapy. Blood tests and/or needle aspirates in many cases are requested to assess tumor control. Any time you suspect a brand new or recurrent tumor, or your dog is physically ill, contact us immediately. We welcome the opportunity to assist you to and your dog in any manner we can.