As our pups get older, many become more likely to develop certain types of cancer. Skin cancer is sometimes easily detected when a new lump or bump appears, and this prompts a trip to your veterinarian to find out more information.
Early detection is key in finding the right treatment, but how can dog owners detect the types of cancer that you can’t see?
What is lymphoma in dogs?
Lymphoma is one of the most common types of cancer and accounts for roughly 20% of all cancer cases. It affects the lymphatic system which is made up of several different components. These are the lymph nodes, the lymphatic vessels, and certain organs like the spleen.
The lymphatic system is responsible for maintaining fluid balance and helping the body fight infection and inflammation.
Lymph nodes release a particular kind of white blood cell known as a lymphocyte which is an important part of how your dog’s immune system functions. In cases of lymphoma, lymph nodes release immature lymphocytes known as lymphoblasts. However, instead of proceeding to normal maturation, they are completely irregular and begin to grow out of control.
When skin cancer occurs, out-of-control cell growth might only be confined to one tumor, but the out-of-control growth with lymphoma can affect your dog’s entire body.
There are four different kinds of lymphoma. Over 80% of canine lymphoma patients have themulticentric or systemic form of lymphoma. This causes your dog’s peripheral lymph nodes to swell up, and these are located in places where you can feel them such as under his chin, in front of his shoulders, and behind his knees.
Alimentary lymphoma affects the gastrointestinal tract, and this is the most common type of lymphoma to affect cats.Mediastinal lymphoma is rare and affects organs in the chest like the perihilar lymph nodes and the thymus.Extranodallymphoma is also rare and affects a specific organ that is not affiliated with the lymphatic system, e.g. the kidneys, lungs, or skin.
Symptoms of dog lymphoma
Signs of lymphoma can be subtle in some cases. At first, you may notice that your dog is more tired than normal, and he may pant a lot even while at rest. Panting can turn into coughing and trouble breathing, and there are even some patients who might experience a seizure even if they’ve never had one before! These are especially common for dogs with multicentric and mediastinal forms of lymphoma.
Dogs with the multicentric form of lymphoma may have swollen peripheral lymph nodes. The easiest to feel are the ones below the chin/neck region and behind the knees. These are often difficult to detect when normal-sized, but swollen lymph nodes will be more obvious.
Other peripheral lymph nodes include the prescapular lymph nodes (in front of the shoulders) and the lymph nodes below the armpits and groin areas. It can be difficult to feel the lymph nodes of the intestinal tract, but these may show up on x-ray or ultrasound imaging.
Lymphoma patients can also experience vomiting, diarrhea, and severe weight loss. This is especially true for patients with the alimentary form of lymphoma. Extranodal lymphoma can affect one particular organ, and so if your dog is suddenly showing signs of a specific illness like kidney disease, it is important to consider kidney orrenal lymphoma on the list of possibilities.
Diagnosis of lymphoma in dogs
Fine needle aspirate is one of the easiest ways to help diagnose lymphoma. Peripheral lymph nodes can become enlarged due to infection and inflammation, so it is important to rule out other diseases before diagnosing lymphoma.
Your vet will use a needle and syringe to collect cell samples from the enlarged lymph node, and sedation is often not necessary for this procedure. If many irregular lymphoblasts are observed on the microscope slide, it is very likely that your pup has lymphoma. If the aspirate is inconclusive, biopsy is often necessary.
Your vet will also recommend baseline lab work like blood and urine testing to make sure your dog’s internal organs are functioning well. X-rays are especially recommended in cases where pets are coughing or having trouble breathing.
Specialized testing such as immunohistochemistry and flow cytometry are recommended to help distinguish B-cell lymphoma from T-cell lymphoma, the latter of which carries the worst prognosis.
Treatment of lymphoma in dogs
Just like in humans, dog lymphoma is treated with chemotherapy and steroid. The most effective type of chemotherapy is known as the CHOP protocol, which involves a combination of three chemotherapeutic agents that alternate weekly and then one steroid medication.
The CHOP protocol is one of the most effective means of treating lymphoma and has the longestmedian survival time, about 12 months. The median survival time (MST) refers to how long a patient survives after treatment is given. For an MST of 12 months, this means that the chance of surviving beyond that specific time is 50%.
There are other variations to chemotherapy protocols, and sometimes surgery and/or radiation therapy are implicated in lymphoma cases. Your veterinarian may be able to help with some of your dog’s chemotherapy treatment, but many dogs benefit from being referred to veterinary oncology specialists. This is because chemotherapy can be tricky, and it takes many months of treatment before dogs can go into remission. Dogs who have had lymphoma once may get it again in future.
Dogs may develop vomiting, diarrhea, or anorexia with chemotherapy, but not all dogs experience side effects. Unlike in humans, hair loss is not a side effect. Dogs who take prednisone as part of their treatment protocol may experience increased thirst and urination. Certain chemotherapeutic agents may be harmful if your dog has existing medical conditions. For example, doxorubicin hydrochloride (the “H” in CHOP), can be risky if your dog has heart disease.
Most chemotherapy protocols are spread out over the course of six months, and it can be very expensive for a lot of owners. If chemotherapy isn’t an option for your pup, your vet can prescribe prednisone by itself. It won’t treat your dog’s lymphoma, but it can help keep him comfortable and is very inexpensive. Treatment with prednisone alone has an MST of 4-6 weeks.
Lymphoma is often a systemic kind of cancer, especially since the most common form of lymphoma is the multicentric type. Early detection can be difficult because it can cause problems internally before you begin to notice enlarged peripheral lymph nodes.
If your dog is showing signs, make sure to contact your veterinarian as soon as possible to get your dog tested. Early intervention can prevent it from spreading and will increase the chances of a good median survival time.
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Meet The Author
Dr. Erica Irish
Erica has worked in the veterinary field since 2006, starting out as a veterinary technician before graduating from the UF College of Veterinary Medicine in 2013. As a general practitioner in an animal hospital, she has many interests and is especially interested in dermatology, cardiology, internal and integrative medicine.