LYMPHOMA

From the textbook of Veterinary internal Medicine - Client Information Series. By Susan A. Kraegel

Lymphoma is a cancer of a specific white blood cell called the lymphocyte.

Lymphocytes are found throughout the body in blood and tissues and act to protect the body from infection. Lymphocytes are the major cells found in lymph nodes or "glands." In lymphoma, the cancer cells invade and destroy normal tissues. The most common site for lymphoma is the lymph nodes, but lymphoma cells, like lymphocytes, can grow anywhere in the body. In most dogs with lymphoma, the cancer cells are present in multiple lymph nodes and tissues.

Chemotherapy is the treatment of choice for almost every dog and cat with lymphoma. Chemotherapy is the administration of drugs by injection or by mouth to kill cancer cells. The chemotherapeutic drug circulates throughout the body. This is important for lymphoma because the cancer cells are in many places at once. Surgery and radiation therapy are less useful in lymphoma because these treatment methods attack cancer cells at only one site.

The goal of chemotherapy for animals with lymphoma is to induce a complete "remission" by killing most of the cancer cells. "Remission" means that all symptoms of the cancer have temporarily disappeared. Animals with Lymphoma that are in complete remission look like normal animals by all tests. They do not have any signs of cancer, and all masses or lumps have disappeared. They eat, drink, and run just as they did before they developed cancer. Some of the cancer cells do survive in an animal in complete remission, but the numbers are too small to detect. Eventually, these few cells will grow and the cancer will become evident again. When this happens the animal is said to be "out of remission." Sometimes a second remission can be achieved with additional chemotherapy. Eventually, the cancer cells will become resistant or insensitive to all drugs and cause the dog to die.

Veterinarians use many different drugs and drug combinations called "protocols" to treat lymphoma in dogs and cats. No one knows the "best" treatment, and many protocols give similar results. In general, the longest survival times are reported for protocols that use a combination of drugs and include more expensive drugs.

Although chemotherapy does not cure dogs and cats with Lymphoma, in most it does extend the quantity and quality of life. About 80 to 90 per cent of dogs with lymphoma attain a complete remission with an average survival of 1 year, and 25 per cent of dogs live 2 years.

Veterinarians use chemotherapy to give dogs with lymphoma a good quality of life with minimal side effects. Most dogs with lymphoma feel good even though they are receiving chemotherapy. The potential for side effects does exist, however, and varies with the protocol used. The most common side effects include decreased energy, decreased appetite, vomiting, and diarrhoea.

Occasionally, more severe side effects occur, and in rare cases an animal receiving chemotherapy will die as a result of treatment. Unfortunately, the only way to know whether an animal is going to have a drug reaction is to give the drug. Some animals never get sick during chemotherapy, but others are very sensitive to the drugs. If your pet has a serious reaction, the drugs or doses your pet receives may be individually adjusted to maintain a good quality of life.

As an owner, you can help your pet with lymphoma by watching the pet closely after each treatment. Chemotherapy will suppress your pet's immune system and make him or her more susceptible to infections. These infections generally arise from bacteria that normally live in the intestinal tract and on the skin, not from the environment. Signs of an infection may include loss of appetite, vomiting, diarrhoea, decreased activity, or depression. Phone your veterinarian immediately if your pet appears ill while receiving chemotherapy. These signs are usually only brief reactions to the drugs, but prompt treatment can often prevent more serious side effects from developing.

OSTEOSARCOMA

From the textbook of Veterinary internal Medicine - Client Information Series. By Susan A. Kraegel

Osteosarcoma is the most common type of bone cancer in dogs. This cancer most often affects large, middle-aged dogs weighing more than 40 pounds. Osteosarcoma can occur in any bone (e.g., rib, skull, toe) but the most common sites are the ends of leg bones, especially at the wrist, shoulder, knee, and hip. The causes of osteosarcoma are unknown, but genetics and microscopic injury to the ends of the bone during growth play a role.

Osteosarcoma begins in the bone but spreads to the lungs and other organs early in the course of disease, even before the initial cancer in the bone is detected. This spread of cancer is called metastasis. In 5 per cent of dogs with osteosarcoma, these metastases are visible on a chest x-ray when the dog is first brought in for the bone cancer.

In over 90 per cent of the dogs with osteosarcoma, these metastases are present but are too small to be seen on the initial x-ray. They are termed "micrometastases."

The first sign of osteosarcoma is generally lameness caused by pain from the cancer. The lameness may come and go and vary in severity from dog to dog. In some dogs the leg may fracture at the cancer site. As the cancer grows, a swelling at the site will also develop, which you may be able to feel or see.

X-rays are the first step in identifying bone cancer. X-rays can only suggest the diagnosis on the basis of the appearance of the bone. X-rays of the chest are also recommended to search for metastases.

Biopsy of the abnormal bone is the only way to diagnose bone cancer absolutely. Side effects of biopsy can include pain, bleeding, and, rarely, fracture of the diseased bone. In 10 to 20 per cent of cases, biopsy may fail to diagnose the cancer, so negative results should be evaluated carefully.

Osteosarcoma is a very aggressive form of cancer in dogs. Oncologists (cancer treatment specialists) have not found a cure. Treatment of both the cancer in the bone and the metastases, however, can give many dogs months to years of good-quality life.

Amputation and chemotherapy are the ideal treatment for dogs with osteosarcoma. The amputation removes the primary cancer and also relieves the bone pain. Most dogs are walking the day after amputation and running soon after. Three-legged dogs have been known to herd cattle and compete in field trials and generally enjoy the same activities as four-legged dogs.

The chemotherapy slows down but does not eliminate the metastases. The chemotherapy currently recommended by most oncologists is usually given once every 3 weeks for four treatments. Most dogs tolerate chemotherapy well and experience only a day or two of mild lethargy or decreased appetite after each treatment. Potentially serious side effects after chemotherapy are uncommon but can include poor to no appetite, vomiting, diarrhoea, blood infection, kidney damage, or heart damage. With amputation and chemotherapy, 50 per cent of dogs are alive at 12 months and 15 to 20 per cent are alive at 2 years. Almost all dogs eventually die from osteosarcoma.

Amputation without chemotherapy provides only pain relief. The metastases continue to grow until they cause death. Only fifty per cent of dogs are alive 4 months after amputation alone and 5 to 10 per cent are alive at 1 year.

In rare cases, amputation may not be advised by your veterinarian. Dogs with pre-existing disease in other legs or severe obesity may not do well after amputation. One option for these dogs is limb-sparing surgery instead of amputation. This is generally possible only when the cancer is in the front limb in the bone called the radius. With this procedure, the cancerous bone is removed, replaced with bone from a dead dog, and the wrist joint is fused so that it cannot bend. Recovery takes 1 to 2 months and infections are common. Survival times are the same as for amputation. For dogs unable to benefit from surgery at all, radiation therapy may be offered as a treatment to relieve pain. Radiation is given over a 3-week period and reduces but does not eliminate pain in about 30 per cent of dogs. The improvement lasts for about 4 to 5 months in these dogs. This therapy increases the likelihood that a dog will break the limb at the cancer site.

Dogs who do not receive any therapy for osteosarcoma are in pain and have a poor quality of life. This pain continues to progress and, according to people with bone cancer, is severe and uncontrollable. Common painkillers do not work. Euthanasia is generally the only humane choice

MAST CELL TUMOURS IN DOGS

From the textbook of Veterinary internal Medicine - Client Information Series. By Mona P Rosenberg

Mast cell tumours are common on or just under the skin of dogs. Any breed of dog can develop a mast cell tumour (MCT), but certain breeds are predisposed, including Boxers, bulldogs, pugs, Boston terriers, golden retrievers, and cocker spaniels. Mast cells are normal cells within the body that are responsible for responding to allergic reactions. For example, if a bee stings you and the area becomes red, hot, and itchy, it does so because mast cells infiltrate into the area, releasing a variety of substances including histamine, causing these symptoms. Other than hereditary factors, we do not know why dogs develop these tumours.

Your veterinarian may have diagnosed this tumour on the basis of a procedure called fine-needle aspiration. This is a minimally invasive technique that involves sticking a needle into the tumour, sucking a few cells out, and smearing the cells on a slide for a pathologist to evaluate under a microscope. This procedure is not painful to your dog and allows us to make a diagnosis in most cases. It does not, however, allow us to predict the biologic behaviour of ("prognose") MCTs; surgical removal of the tumour followed by the use of a grading system is required. Location of the MCT is also of prognostic significance.

Knowing that we are dealing with an MCT before surgery can be helpful, because MCTs are notorious for sending out long, finger-like projections of cells into the surrounding tissue. This means we must surgically remove a wider margin of "normal" tissue surrounding any visible tumour in an attempt to remove all the microscopic "fingers."

Grade I or well-differentiated MCTs are the least aggressive of the three classes. If we are able to surgically excise the entire tumour (the pathologist will comment that the margins of tissue removed are "clean" or free of cancer cells), the incidence of recurrence is typically small, with 93 per cent of dogs being disease free at 1 year. "Metastasis" or spread of this form of MCT to distant, internal locations is unusual.

Grade II or intermediately differentiated MCTs are more aggressive than their grade I counterparts. An as yet unidentified percentage of dogs with this form of MCT develop metastasis of their cancer to internal organs, typically to the bone marrow, spleen, or local lymph node. Provided there has been no spread of the cancer, 50 per cent of dogs with completely excised grade II or intermediately differentiated MCTs develop recurrence within 10 months of diagnosis; if no recurrence is detected in this period of time, there is a very good chance that the dog will survive for 5 years free of tumour.

Grade III or poorly differentiated MCTs carry a very poor prognosis, with 97 per cent of dogs succumbing to their cancer by 1 year. This is due to the high rate of metastasis or spread of the cancer to internal organs.

Mast cell tumours in the groin behave similarly to grade III MCTs, regardless of their histologic grade. It is not currently understood, but a high potential for metastasis has been consistently observed. Some oncologists believe that MCTs in the armpits and mucocutaneous junctions (e.g., lip margins, vulva, anus) can be quite malignant as well.

Once a dog is diagnosed with a MCT, several diagnostic tests are recommended. First, a complete blood count, bio-chemical profile, and urinalysis are performed to ensure that your dog exhibits no negative effects of the cancer in his or her system. Sometimes, a blood test called a buffy coat test is performed. This test looks for mast cells circulating through the bloodstream. This test is useful if it is positive, but it is often negative even if the cancer has spread; thus, it is not very sensitive.

The next step is to grade the cancer if this has not yet been done. Again, this can be done only by surgically removing all or part of the tumour. Once the tumour grade is known, a decision regarding further testing and treatment can be made. If the local lymph node is enlarged, it will be aspirated to look for cancer cells. If the MCT has been graded as intermediate or poorly differentiated (grade II or III), aspiration of the bone marrow and the spleen is advised. This is the most sensitive technique for determining whether the cancer has metastasised. Unfortunately, dogs with mast cell cancer in the bone marrow or the spleen have a very poor prognosis; many dogs live only 90 days from the time of diagnosis because of the effects of the cancer cells on the body. Sometimes, even in dogs with advanced disease, treatment can improve both the quality and quantity of life.

Your veterinarian may refer you to a cancer specialist for the testing or further discussion of your options for treatment.

Treatment for dogs with MCTs is dependent on the grade of tumour and results of testing. Dogs with grade I tumours that have been completely excised (removed) are not typically treated with any additional therapy. The "gold standard" of treatment for dogs with grade II MCTs, because of their moderate incidence of local recurrence even with complete surgical excision, is radiation therapy.

We also recommend using radiation therapy to treat grade II tumours and I that cannot be completely excised, provided there is no evidence of metastasis. Eighty-eight per cent of dogs with incompletely excised grade II tumours survive for 5 years without disease when treated with radiation therapy.

For dogs with grade III MCTs, dogs with MCTs in the groin, or dogs that have been diagnosed with systemic spread of their mast cell cancer, drug therapy is often recommended. These drugs include diphenhydramine (Benadryl) and cimetidine (Tagamet) to counteract the effects of histamine on the body and prednisone and other chemotherapy drugs to attempt to kill the cancer cells.

These drugs are usually well tolerated by dogs. Signs of terminal stages of the cancer include lethargy and gastrointestinal signs such as vomiting, diarrhoea, and poor appetite.

Our goal for all cancer patients is that their quality of life be excellent; we never want the treatment to be worse than the disease. This goal is often achieved by working as a close team with your veterinarian and often a board-certified cancer specialist.

WHAT TO EXPECT WHEN YOU GO TO THE VET WITH A DOG WHICH HAS LUMPS, BUMPS, TUMOURS OR CANCER

Your dog is 35 times more likely to suffer skin cancer than you are, four times as likely to develop a breast tumour, eight times as likely to suffer bone cancer, and twice as likely to develop leukaemia. 

SOME GENERAL COMMENTS

Like many of the treatment pages on this site, I'll start with a few general comments and then try to describe what would happen if you brought your pet into our clinic for treatment...in this case for a mass.

After that, I will soon try to compile as many interesting...or at least informative...articles, comments and links as possible in order to give you a good general background education about cancer and masses in pets.

I hope you aren't reading this page because your pet is in serious trouble.  If so, you have my sympathy and prayers.

LUMPS, BUMPS AND CANCER IN DOGS

Unfortunately, cancer is fairly common in pets. The good news is that a lot of the common masses we detect in veterinary medicine that you may think of as cancer are benign.

More good news is that more and more medical advances are being made in the treatment and control of different cancers; so there is hope.

CUTANEOUS AND SUB-CUTANEOUS LUMPS, BUMPS AND MASSES

A lot of dog and cat patients come in for exams because of various lumps and bumps on or under the skin in their pet. In the veterinary business, that's just what we call them; lumps and bumps.

Thankfully, most are not serious, but, of course, that's not always the case.

WHAT TO EXPEXT IF YOU GO TO THE VET
(Your vet may do things differently)

 A Good Exam & History: In addition to our normal through exam we will be especially careful to note how long these masses have been there, have they gotten bigger or changed much over time, do they hurt and so forth.

Are the nearby lymph nodes enlarged?

Do they feel fluid filled or solid?

Is the mass mobile or firmly attached?  Is it spherical or irregular in shape?

Are they just moles or warts or cysts?

Are they just fatty tumours which are fairly common in middle aged and older dogs?

Are they related to recent injections?

Are they related to skin inflammation or ingrown hairs?

Or are these lumps and bumps possibly cancer? And, if so, metastatic and malignant? Or benign? These are the big questions that we will want to answer.

Often, an experienced veterinarian can assure you with great (but never perfect) accuracy on physical exam alone that a bump is not serious. Other times, it won't be obvious and testing will be appropriate.

If needed, here's what we'll recommend:

Diagnostics:
1. After cleaning and clipping hair if needed, we'll stick a small needle in the lump and see what comes out and look at the fluid if present under the microscope. This simple test will help confirm if the mass is just a fatty tumour, cyst, or abscess. The cost in our hospital is $0-15 depending on whether we use lab stains and fixation or just look at the aspirate directly.

If the lump is a small abscess or cyst, we will often "lance" and express and hopefully cure the problem on the spot. This costs $0-15 depending on how much fun we have. Other times local or general anaesthesia and minor surgery is needed to get the job done right and that's more expensive.

2. If no fluid comes out when we stick a needle into the lump or the lump is too big or deep to make a needle stick an appropriate test (an example are the chain of lumps found in breast tissue), or if the fluid is suspicious, then cytology and/or biopsy are appropriate.

Some vets do this in house; I send them to a lab. Since to get a biopsy involves anaesthesia (unless very superficial), we often surgically remove the mass at the same time. 

3. Radiographs are often appropriate and if your veterinarian has an Ultrasound, he or she may want to use it to better define the mass.

4. Blood work is not likely to be needed for the diagnosis of the lump or mass itself, but, of course, would be wise for several reasons: Cancer, if present may be affecting internal organs.  Routine blood work will tell us whether or not there is anaemia and/or infection present ... both fairly common in conjunction with cancer, and lastly, we like to make sure the internal organs are functioning normally prior to anaesthesia which we'll probably need for biopsy or removal of the mass.

Treatment Options
A. We might decide to do nothing except monitor if we think the mass is one of the many typical benign masses we veterinarians see on a regular basis. $0-1,000 depending on how many times you ask me if I'm absolutely sure it's not cancer (just kidding about the cost...but not being sure is the problem with not doing lab work, isn't it?)

B. Simple lancing or removal under local anaesthesia if small enough.

C. Anaesthesia and Surgical removal. I do this the old fashioned way...with scalpel and scissors...other vets might use a surgical laser or even "freeze" the mass. These methods sometimes have advantages but are generally more expensive.

Cost at our hospital all depends on the size and location of the mass and the difficulty and extent of follow up care (dealing with surgical drains, for example) 

D.  Post op antibiotics and medications for pain and inflammation if needed

E.  Recheck. Remember that masses can be unpredictable and recur.

Deal with the biopsy results if not benign: Choices here are fairly limited;

A. Pray that I removed 100% of the mass (often unrealistic) and it won't come back or isn't already somewhere else in the body.

B. Make the patient comfortable and treat minor secondary problems and maximize the delay of major problems through aggressive nutritional support etc...sometimes there's a long time of quality life prior to eventual deteriation.

C. Referral to an oncologist. Great strides have been made in the treatment and control of some malignant cancers. Cancer therapy can be expensive and have unfortunate side effects and can often be futile, but not always, especially for certain types of cancer...so please give this option some thought.

 D.  Consider Alternative Medicine.  I personally don't have a lot of faith in most of the alternative treatments being heavily promoted to the new age crowd...but who knows?