Overview of Canine Liver Cancer
Hepatic neoplasia is cancer of the liver which can occur in dogs. The words cancer, neoplasia or neoplasm, and tumor are often used interchangeably. Neoplasia in the liver may be the result of a primary liver tumor (one that originates in the liver), hemolymphatic cancer (arising from blood cells or lymphoid tissue) that involves the liver, or metastatic cancer (cancer that has spread to the liver from other organs).
The most common form of liver cancer in dogs is metastatic disease. Primary liver cancer is rare, comprising less than two percent of all cancer seen in these species. When it does occur, the most common primary liver tumors seen in dogs are hepatocellular carcinomas, which are malignant tumors that arise from the liver cells, and hepatocellular adenomas or hepatomas, which are benign tumors that arise from the liver cells.
The cause of primary liver cancer may be related to environmental factors. Exposure to carcinogens, or cancer-causing chemicals, may increase the risk of cancer development. Many chemicals are not toxic until they are metabolized by the liver. The liver serves an important role in detoxifying many substances circulating in the body. However, some chemicals are made more toxic after they have been broken down by the liver. Examples of possible carcinogens include toxins produced by fungi that are sometimes associated with spoiled pet food, food additives, certain pesticides, dyes, plants and animal tissue. Viral infections have been associated with hepatic cancer in humans. This has not been shown in dogs.
Primary liver cancer is most common in pets greater than 10 years of age. There is a slightly increased risk of hepatocellular carcinoma in males compared to females.
The impact of the disease on the pet varies depending on the tumor type. Benign tumors do not spread and generally do not cause illness unless they are physically impinging on other abdominal organs, or if they rupture and bleed. Occasionally, large benign liver tumors cause hypoglycemia (low blood sugar) by probable release of insulin-like substances. Insulin is the hormone that controls blood sugar levels, and is normally produced by the pancreas.
What to Watch For
Signs of liver cancer in dogs may include:
Increased respiratory rate
Jaundice (yellow discoloration of the skin)
Malignant tumors carry a much graver prognosis as these are aggressive disease processes and often have evidence of widespread involvement by the time of diagnosis. Just as other tumors can metastasize to the liver, primary liver tumors can metastasize to other organs. The symptoms are often vague and non-specific.
Diagnosis of Hepatic Neoplasia in Dogs
History and physical exam
Complete blood count (CBC)
Abdominal radiographs (x-rays)
Thoracic (chest) radiographs
Coagulation profile (clotting tests)
Treatment of Hepatic Neoplasia in Dogs
Medical stabilization, which may require IV fluids and blood transfusions in certain cases
Surgical mass removal when possible
Chemotherapy, depending on the tumor type
Home Care and Prevention
Administer all medications as prescribed by your veterinarian. Monitor your pet for abdominal distension, pale gums, extreme weakness, anorexia, vomiting or diarrhea.
Feed a high quality pet food and provide proper storage to insure freshness of the food. Discard any food that appears to be spoiled.
In-depth Information on Hepatic Neoplasia in Dogs
Although hepatocellular tumors and tumors of the biliary tract are the most common primary liver tumors, other tumor types may also occur. These include:
Hemangiosarcoma – a malignant tumor that originates from blood vessels
Hemangioma – a benign tumor that originates from blood vessels
Fibrosarcoma – a malignant tumor that originates from connective tissue
Leiomyosarcoma – a malignant tumor originating from smooth muscle
Carcinoids – a malignant tumor arising from specialized endocrine cells.
Hemolymphatic tumors that often involve the liver include:
Lymphosarcoma – a tumor of the lymph nodes and lymphatic tissue
Mast cell tumors – mast cells are involved in allergic responses and can become malignant and form tumors
Leukemia – cancers that arise from blood cells
Multiple myeloma – a type of cancer that arises from specialized antibody producing cells
The liver is the most common organ involved in metastatic disease, or spread of malignant cancer. Many tumor types may metastasize to the liver. Because the symptoms of hepatic neoplasia are often quite vague, there are any number of other disease processes that may cause similar signs. In cases of metastatic disease, the signs are often related to the site of the primary cancer. Generally the initial diagnostic work-up allows recognition of some type of liver problem. Other liver diseases that may cause similar symptoms include:
Hepatitis or cholangiohepatitis. These are inflammatory conditions of the liver, or liver and biliary or bile transport system.
Hepatic abscesses. Abscesses in the liver are bacterial infections with associated pockets of pus similar to an abscess your pet could develop in the skin.
Hepatic hematomas. Hematomas are large collections of clotted blood that may occur in the liver secondary to trauma or secondary to ruptured portions of the liver. The hematomas usually do not cause clinical problems unless they begin to bleed profusely.
Hepatic necrosis. Necrosis or cell death of the liver may occur secondary to toxins or adverse drug reactions.
Leptospirosis. This is an infectious liver disease of dogs, caused by a particular type of bacteria called a spirochete. It can cause both liver and kidney damage and subsequent inflammation of these organs.
Hepatic flukes. Flukes are parasites that invade the liver. They are quite rare.
Hepatic viral infections. Viruses that target the liver include canine infectious hepatitis virus in dogs. As with other infectious causes, these animals usually have more than one body system involved.
Fungal infections. Systemic (widespread) fungal infections can involve the liver. Individual fungi are limited to certain geographic regions of the United States.
Liver lobe torsion. In rare instances, part of the liver may become twisted. This may happen following trauma or can occur spontaneously.
In-depth Information on Diagnosis
A thorough history and physical exam are important in order to establish a diagnostic plan. Since the clinical signs of hepatic neoplasia can be quite vague, the physical exam is an important diagnostic tool. Many animals with hepatic neoplasia have an enlarged liver or a palpable mass in the abdomen. Free fluid in the abdominal cavity can also be recognized on physical exam, which may be an indication of bleeding into the abdomen or other fluid accumulation that is sometimes seen with liver disease. Physical exam may also suggest anemia (low red blood cell count) or reveal jaundice based on the appearance of the mucous membranes (gums, whites of the eyes).
Complete blood count. The CBC evaluates the red and white blood cells, as well as the platelets. Dogs with liver neoplasia may be anemic, especially if they have had internal bleeding. Red blood cell morphology (shape) may also be affected with certain tumor types. Elevations of the white blood cell count may also be noted, but this is a non-specific finding. Atypical or cancerous white blood cells may be seen in animals with hemolymphatic neoplasia. Animals that have had internal bleeding may also have reduced platelet numbers, as platelets are necessary for normal blood clotting and may be consumed when bleeding occurs.
Biochemical profile. The biochemical profile provides important information with respect to the liver. The enzymes produced by the liver are often elevated with hepatic neoplasia. Additionally, liver function can be partially assessed by measuring albumin (a blood protein made by the liver), blood sugar, bilirubin (a breakdown product of red blood cells that may be elevated with liver dysfunction, which results in jaundice), cholesterol, and blood urea nitrogen (a substance made in the liver from metabolism of protein). All of these parameters are measured on the biochemical profile. It is important to note however that abnormalities in these measurements can be seen with any type of liver disease and are not specific indicators of neoplasia.
Abdominal radiographs. Radiographs provide good information with respect to liver size and the presence of masses in the abdomen. Small masses may not be seen with routine radiographs. Fluid accumulation in the abdomen can also be noted on radiographs.
Thoracic radiographs. Radiographs of the thorax are important in cases where neoplasia is suspected, as the lungs are a common site of metastasis for many tumor types. Although metastatic disease can be present without showing up on the radiographs, the presence of metastasis in the lungs that is noted radiographically indicates that the disease has definitely spread to the lungs.
Abdominal ultrasound. Ultrasound often complements the findings on abdominal radiographs. It is a more sensitive means of examining the liver architecture. Additionally, it may be able to detect smaller masses, as well as evidence of locally enlarged lymph nodes and abnormalities in other abdominal organs. It is not as good at judging liver size compared to radiographs.
Coagulation profile. Tests of clotting function are imperative in animals with liver disease. The liver is responsible for making the vast majority of the body’s clotting factors, so with liver dysfunction clotting can be abnormal. It is not common for animals with primary liver tumors to have defects in clotting ability, although it is important to test this prior to any invasive diagnostics, in order to assess the risk of bleeding. Additionally, if the tests are abnormal, specific therapy may be indicated.
Liver biopsy. Biopsy of the liver is necessary to make a diagnosis of hepatic neoplasia. Appearance of the liver alone is not a reliable method of diagnosis of neoplasia. With certain types of neoplasia, most notably the hemolymphatic cancers, diagnosis is made by fine needle aspiration and cytologic analysis (microscopic evaluation of the cells). However in the majority of cases, actual liver tissue must be obtained for microscopic review. This is important because an erroneous diagnosis of liver cancer might otherwise be made. The method used to obtain the biopsy may vary depending on the stability of the patient as well as the appearance of the masses associated with the liver and whether or not there appears to be multi-organ involvement. Biopsies may be obtained via ultrasound guidance, in which the abdomen is not opened; laparoscopy, using a small scope and biopsy instrument that are placed into the abdominal cavity; or abdominal surgery.
In-depth Information on Therapy
Therapy for the common primary hepatic neoplasms includes:
Medical stabilization. Unstable animals or severely dehydrated animals may require medical stabilization prior to liver biopsy. This might include intravenous administration of fluids, as well as blood transfusions in animals that are severely anemic. In dogs that have evidence of severe and sudden blood loss into the abdominal cavity, an external pressure wrap is placed around the abdomen to aid in stopping the bleeding. Animals that show a deficiency in their coagulation tests may require plasma therapy – the constituent of the blood that does not contain red blood cells – to replenish clotting factors.
Surgical removal of liver masses. This is the treatment of choice, whenever possible. The feasibility of mass removal depends on the nature of the tumor. Many hepatocellular carcinomas are solitary masses. If they have not spread throughout the liver, partial removal of the liver can be performed. As much as 80 percent of the liver can be removed without causing harm, if the remaining liver is normal. Hepatocellular adenomas are usually surgically removable. Bile duct carcinomas are very difficult to remove, and have usually spread by the time of detection. Bile duct adenomas can often be treated by surgical removal.
Chemotherapy. This is a recommended treatment for many tumors that involve the liver, although it has not been shown to be useful for primary malignant hepatic neoplasia. Unfortunately these tumors tend to be highly resistant to chemotherapy drugs. This is also the case in human hepatic neoplasia.
Follow-up care for Dogs with Liver Tumors
Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your dog does not rapidly improve.
Administer all prescribed medications as directed. Alert your veterinarian if you are experiencing problems treating your dog. This applies to all forms of hepatic neoplasia, as there are no home treatments for primary hepatic neoplasia.
If your pet has a benign liver tumor or a tumor that can be surgically removed, the long-term prognosis is good. Dogs with hepatocellular carcinoma have an average survival time of slightly more than one year following surgery. Many dogs will live several years. Following surgery your pet should be monitored for recurrence of the signs that alerted you to a problem in the first place. These may include anorexia, lethargy, weakness, pale gums, vomiting, diarrhea and abdominal distension.
Follow-up care with your veterinarian following surgery may include a CBC and biochemical profile to look for normalization of liver enzymes and resolution of a previous anemia or elevation in the white blood cell count. In patients with a diagnosis of malignant liver tumors, serial thoracic radiographs and abdominal ultrasound may be indicated to look for evidence of metastatic disease.
Malignant tumors that cannot be surgically removed due to severe involvement of the liver and/or metastatic spread to other sites carry a very poor prognosis.