Liver Cancer in Dogs
A pet diagnosed with cancer is every dog owner’s worst fear. There are many types of cancer, and some are more serious than others. Liver cancer in dogs is uncommon, but it is often serious. Most cases of liver cancer in dogs spread to the liver from another tumor elsewhere in the body. Once a tumor metastasizes like this, it’s a lot harder to remove and the prognosis is poorer.
Let’s take a look at liver cancer in dogs, and what dogs with liver cancer can expect in terms of treatment and life expectancy.
What is Dog Liver Cancer?
Dog liver cancer occurs when cells in the liver grow out of control. Depending on the type of cell involved, this can cause a large lump (tumor) on the liver or be spread throughout the liver so that the whole liver is slightly enlarged.
In some cases, the cancer can start in the liver – called a “primary” liver tumor. Primary liver cancer in dogs is very rare. However, because the liver filters a lot of blood, it’s more likely for cancer to spread to the liver from other tumors in the body. This is called a “secondary” liver tumor. It’s thought that secondary tumors are 2.5 times more common than primary tumors in the liver.
Like most cancers, dog liver cancer generally affects older dogs. While liver cancer can affect all breeds, Labrador Retrievers are slightly more prone to a type of cancer called a bile duct carcinoma, while Miniature Schnauzers are more likely to get hepatocellular carcinoma. Some types of liver cancer are thought to be more common in males, while some are thought to be more common in females.
Causes of Liver Cancer in Dogs
Primary liver cancer often doesn’t have a known cause in dogs. It’s likely to be a random mutation in the cell DNA, with several mutations eventually leading to cancer. We know that older dogs are more at risk, which fits with this theory as the mutations add up until they eventually cause cancer.
In rare cases, liver cancer of the bile ducts may follow a parasitic infection of the liver. Although toxins are often blamed for liver cancer in dogs, there is no scientific evidence that toxins cause liver cancer in our canine friends. Neither is there any evidence that dog liver cancer is caused by their diet.
Secondary liver cancer is more common in dogs. This is liver cancer that starts elsewhere in the body but spreads to the liver. For instance, tumors of the spleen or pancreas often spread to the liver. This means the liver cancer has been caused by the other tumor, which complicates the risk factors – in theory, every cancer risk (such as obesity) could increase the risk of secondary liver cancer.
Liver Cancer in Dogs Symptoms
About 75 percent of dogs with liver cancer show symptoms of a problem. This means that a quarter of cases are “silent” and can go a long time before being diagnosed. When symptoms are seen, they are vague and often fluctuate, which can also lead to dogs not being diagnosed quickly.
The symptoms of liver cancer in dogs include:
- Weight loss
- Nausea and vomiting
- Drinking more
- Urinating more
- Swollen, fluid-filled belly (ascites)
- Yellow-colored eyes, lips, and other mucus membranes (jaundice)
- Disorientation, wobbliness, circling, head-pressing (rare)
- Seizures (rare)
Types of Liver Cancer in Dogs
Liver cancer in dogs is categorized several ways. Firstly, there’s whether the cancer is primary (originates from the liver), or secondary (originates elsewhere in the body). Next, we can talk about where the tumor is and what it looks like – called massive, nodular, and diffuse. Lastly, tumors are also categorized by what cells they’re made up of. Let’s look at types of liver cancer in dogs in more detail:
Primary and Secondary Liver Cancer
As discussed above, dog liver tumors can be either primary or secondary. Secondary tumors start elsewhere (commonly the neighboring organs of the gut, pancreas, or spleen) and spread (metastasize) to the liver. Primary liver tumors are those that start in the liver.
Secondary liver cancer is much more common than primary, so if cancer of the liver in dogs is suspected, your vet will also look elsewhere to see if there are any other tumors present. If the liver tumor is found to be secondary to another mass, the cancer is named after the organ it originates from – for instance, “pancreatic cancer with liver metastases.”
Massive, Nodular, and Diffuse Liver Cancer
Of the primary liver cancers, the tumor can then be categorized as:
Massive means there is a large, single tumor, affecting only one lobe of the liver. When examined with the microscope, the abnormal cells are all in this lump – just millimeters away, completely normal liver cells are seen. This is the most common type, which is a good thing. These types of tumor are slow to metastasize and easier to remove surgically, granting a good prognosis.
Nodular liver tumors in dogs are generally smaller and there will be several lumps, which are usually evenly dotted around the liver and affecting several lobes. This type of liver cancer is more serious – it metastasizes in over 90 percent of cases. It’s also impossible to remove surgically, and there are no real treatment options.
Diffuse liver tumors are spread throughout the liver. On inspection, you can’t see a clear lump, or even several lumps, but the whole liver will appear strange. When examined with the microscope, cancerous cells are spread evenly throughout the liver. It’s impossible to remove, and — like nodular tumors — there are no good treatment options, meaning diffuse liver cancer carries a poor prognosis.
Dog Liver Cancer Cell Types
Canine liver cancer is also categorized by which cells are involved. Many different cells make up the canine liver, so tumor types include:
- Hepatocellular Carcinoma
- Hepatocellular Adenoma
- Bile Duct Adenoma
- Bile Duct Sarcoma
- Carcinoids (Neuroendocrine Tumors)
- Hepatic Sarcoma
By far the most common of these is hepatocellular carcinoma, sometimes called HCC, which accounts for 50 percent of all primary canine liver cancers. Most HCCs are massive, which means they carry a better prognosis as they can be surgically removed.
Hepatocellular adenomas often don’t cause symptoms – in fact, they’re fairly benign, although they can still cause problems if they rupture (burst) or if they’re large.
Bile duct carcinoma is the second most common liver cancer type in dogs. It’s a more severe cancer though, both being more likely to be nodular or diffuse (and therefore harder to remove) and more likely to metastasize.
The other liver cancer types are rare to extremely rare – hepatoblastoma has only been reported in one dog!
Dog Liver Cancer Stages and Progression
As with all cancers, the earlier liver cancer is diagnosed, the better. The majority of cases will have hepatocellular carcinoma (HCC) and will be massive. This means surgical removal is possible, but it will get harder the bigger the tumor is, and the likelihood of the tumor spreading to other parts of the body is increased.
Diagnosing Canine Liver Cancer
If your veterinarian suspects liver cancer, there are a number of tests they will want to perform. The first is a clinical examination, looking for jaundice and other external signs of a liver problem. They will also feel your dog’s abdomen – in some cases, liver tumors can be felt by palpation. However, if they are not, it unfortunately doesn’t rule out liver disease. Tense, nervous dogs, the position of the liver in the abdomen, and the type of liver cancer can all make it hard to feel what’s going on.
Next, blood tests may help your veterinarian to diagnose liver cancer. Significantly raised liver enzymes will often increase suspicion of liver cancer in dogs, although there are other causes. More specific blood tests, including fasting blood tests, may be ordered. Coagulation tests – checking your dog’s ability to clot their blood – will also be important if liver cancer is likely. Urine samples may also be recommended, especially if your pet has been drinking and peeing more than usual.
Imaging is really important for diagnosing canine liver cancer. The most common form of imaging used is ultrasound (sonogram). Not only can it be done on a conscious animal, but it can see liver tumors large and small, and experienced sonographers may even see diffuse liver cancer. If an ultrasound is not an option, X-ray may see larger liver tumors, or your clinician may recommend referral for a CT scan.
Veterinarians may also take a biopsy of a suspicious area using a needle while doing an ultrasound scan. Alternatively, biopsies may be taken using minimally-invasive techniques (keyhole surgery) or during an exploratory laparotomy. These biopsies can be sent to a specialist laboratory to find out the type of liver cancer your dog has.
Dog Liver Cancer Treatment Options
Treatment is limited for cancer of the liver in dogs. Luckily, the majority of cases are massive HCCs, which respond well to surgery. Since massive tumors are limited to one liver lobe, the dog undergoes a liver lobectomy, where the whole lobe is removed, and – in most cases – the rest of the liver will continue to function as normal. Your dog may need to be placed on a special dog liver cancer diet which will help the liver to cope before and after surgery.
Unfortunately, where liver tumors are nodular or diffuse, there are no good treatment options. Chemotherapy is sometimes used, but is not very successful – many liver tumors are resistant to chemotherapy. When it does work, it’s not curative. While it may slow the progression of the cancer, it will still continue to grow and the liver will still be very vulnerable to rupture (bursting), which will cause huge blood loss.
In some cases, pet parents might simply choose to do nothing – they’ll monitor their dog’s condition, provide symptomatic treatment such as pain relief, a liver diet, or appetite stimulants, and say goodbye when the time is right. This is known as palliative care.
Cost to Treat Liver Cancer in Dogs
Liver cancer can be expensive to diagnose and treat. There’s the cost of the diagnostic tests – since multiple blood tests are necessary, you can expect a bill in the hundreds of dollars.
Imaging will have a further cost, especially if sedation is needed to take X-rays. Biopsies also add to the cost of liver cancer diagnosis. Both of these procedures usually cost in the hundreds of dollars, as well.
Once liver cancer is diagnosed, the cost to treat it depends on the type of tumor. Operating on a cancerous liver is difficult. It takes great skill, specialist equipment, and a good follow-up plan – and is likely to cost in the high hundreds to mid thousands, depending on the difficulty of the operation.
Chemotherapy is also expensive, especially when weighed against the fact it’s unlikely to work.
Prognosis for Liver Cancer in Dogs
Dogs with liver cancer have varied prognosis depending on what type of cancer they have. Massive HCCs have the best prognosis – with successful surgical removal, these dogs can live for four years on average, and often die of an unrelated condition.
If the tumor is not removed surgically, the likely survival time for this type of tumor is less than a year.
On the other hand, diffuse and nodular tumors have a far worse prognosis as they are inoperable and usually chemo-resistant. Palliative care is generally recommended for this type of liver cancer in dogs.
Pet parents of dogs with liver cancer often wonder when to euthanize. This is a personal choice and will depend on your dog’s symptoms and quality of life. A quality-of-life assessment tool can be useful to help you decide when to euthanize your dog with liver cancer. In general, you should think about whether your dog can still do the things they enjoy – in the final stages of liver cancer in dogs, their symptoms may be too severe to allow them to enjoy life.
How to Prevent Liver Cancer in Dogs
Unfortunately, we don’t currently know of any way to prevent liver cancer in dogs, as no causes have been identified. Primary liver cancer is luckily rare – knowing the symptoms and acting quickly if you suspect cancer gives your dog the best chance of survival.