Your dog’s liver plays an important role in their health, from filtering toxins from their blood to helping with digestion. As a result, cancer in dogs can have serious consequences. Some liver tumors are benign, meaning they aren’t cancerous and won’t spread to other organs. But some tumors are malignant (cancerous) and can spread throughout the liver or even metastasize (travel to other areas of the body). Here’s what to know about the signs of liver cancer in dogs, diagnosis, and possible treatments, and the impact liver cancer may have on your dog’s lifespan.
What Is Liver Cancer in Dogs?
Liver cancer is the uncontrolled growth of cells in the liver. Cancer cells can originate in the liver, known as primary liver cancer. When cancer cells originate in another area of the body and settle in the liver, this is known as metastatic or secondary liver cancer, meaning the cancer cells have metastasized or traveled there.
Primary Liver Cancer in Dogs
Primary liver cancer is rarer than metastatic liver cancer. In fact, primary liver tumors only account for about 1% of all canine tumors, benign or malignant. There are four basic types of primary liver cancer, and they’re defined by the cells where the tumor originates. The types of primary liver cancer in dogs are:
- Hepatocellular carcinoma (HCC), which originates in liver cells known as hepatocytes
- Bile duct cancer, which starts in the liver’s bile ducts
- Neuroendocrine tumors, which originate in the hormone-secreting cells
- Stromal tumors, which start in the connective tissues of the liver
Understanding HCC in Dogs: HCC is the most common type of primary liver cancer in dogs, accounting for over half of all primary liver tumors. HCC in dogs can take three different forms, depending on the structure and how many of the dog’s liver’s six lobes are involved. The types of HCC in dogs are:
- Massive tumors: These tumors don’t get their name from their size. Instead, they consist of a single, large tumor that affects only one lobe of the liver. Over half of all HCC tumors in dogs are massive tumors. These are also the easiest to remove, since they aren’t spread throughout the liver.
- Nodular tumors: These tumors involve several masses in two or more lobes.
- Diffuse tumors: These tumors occur when the cancer appears through the entire liver.
Metastatic Liver Cancer in Dogs
Metastatic liver cancer is about 2.5 times more common in dogs than primary liver cancer. In most dogs with metastatic liver cancer, the cancer cells originate in a dog’s intestinal tract, spleen, or pancreas.
However, this condition can also result from cancerous cells in other parts of the body. For example, metastatic liver cancer is associated with pancreatic cancer, thyroid cancer, lymphoma (cancer of the lymphatic system), intestinal carcinoma (cancer of the intestine), fibrosarcoma (cancer of the connective tissue), canine hemangiosarcoma (cancer that causes blood vessels to rupture), and other cancers. After these cancer cells travel through the body, they may end up in the liver. Once in the liver, they can develop into a secondary tumor. In fact, metastatic liver cancer is the cause of most canine liver tumors.
Which Dogs Are at Risk for Liver Cancer?
Primary liver cancer has no known cause, but could result from a combination of factors, such as genetics and environment.
Liver cancer in dogs is usually a disease that affects dogs over 9 years old. In one study, the median age of dogs with benign liver tumors was 11 years old, while the median age of dogs with malignant liver tumors was 12. There is some evidence suggesting that HCC appears more often in male dogs than female dogs and suggestions that bile duct cancer may affect female dogs more than male dogs. But more research needs to be conducted before these claims can be verified. Overall, primary liver cancer seems to affect male and female dogs equally.
As for metastatic liver cancer, certain breeds are more susceptible to cancers that are known to metastasize. These genetic factors may put particular breeds at higher risk for developing cancers that can spread to the liver. For example, Rottweilers are at higher risk of canine lymphoma, and Weimaraners and Golden Retrievers are prone to mast cell tumors, both of which can lead to liver tumors. Because ovarian cancer or cancer of the mammary glands in female dogs is known to metastasize, female dogs might be at greater risk than males for metastatic liver cancer.
What are the Signs of Liver Cancer in Dogs?
Unfortunately, the early stages of liver cancer in dogs don’t usually cause symptoms. It’s only when the tumor has grown to a larger size that your dog will show signs of cancer. Talk to your vet if your dog exhibits the following symptoms:
- Loss of appetite
- Vomiting and/or diarrhea
- Weight loss
- Lethargy and/or weakness
- Increased thirst and/or increased urination
- Ascites (when the abdomen is bloated with fluid)
- Jaundice (yellow tint to the eyes, skin, and gums)
How is Liver Cancer in Dogs Diagnosed?
Your veterinarian will need to conduct multiple tests to accurately diagnose liver cancer in your dog. Blood work and urinalysis can show markers for liver damage or reduced liver function. Your vet will also examine your dogs’ abdomen, looking for signs of pain or discomfort, as well as feeling for an enlarged liver, which can indicate the presence of a tumor. Imaging, such as ultrasounds or X-rays, can verify whether a tumor is present.
If a tumor is discovered, your vet might take a sample of the cancer cells. This can be done with fine needle aspiration (inserting a long, thin needle into the mass to collect some cancer cells) or core needle biopsy (inserting a long, hollow needle into the mass to remove a piece of the tumor). Then, a veterinary pathologist, an expert in examining animal tissue, will examine the sample under a microscope to further identify the cancer.
What is the Treatment for Liver Cancer in Dogs?
The preferred treatment for primary liver cancer is surgery, which removes as much of the tumor as possible (or even an entire lobe of the liver, called a lobectomy). This can relieve symptoms and also prevent the cancer from spreading to other organs. Although a lobectomy can involve removing a large section of the liver, amazingly, the liver can regenerate, allowing your dog a good quality of life.
However, sometimes it’s not possible to remove the tumor, like with nodular or diffuse cancer. In this case, your vet might suggest chemotherapy to extend your dog’s life.
What is the Prognosis for Liver Cancer in Dogs?
The outcome, or prognosis, for a dog with liver cancer depends on many factors. Recent research found that the size of the tumor and the number of affected lobes of the liver have a significant impact on a dog’s lifespan. If your dog has multiple tumors, either primary or metastatic, then the prognosis will depend on the location of the tumors and how much they have invaded the liver tissue.
Another study looking specifically at HCC found no difference in survival time between dogs with different tumor subtypes or differing numbers of lobes involved. The dogs in this study had a median survival time of 707 days (about two years). However, these researchers looked at all three subtypes of primary liver cancer (massive, nodular, and diffuse). In an earlier study examining massive HCC tumors, researchers found that dogs survived for more than 1,460 days (about four years) after removal of the affected lobe.
Although a diagnosis of liver cancer is serious, depending on your dog’s situation and the treatment you choose, your dog could still enjoy a good quality of life for a while.
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