The liver is the most important organ in the body of a dog. It is the central point of almost all activity that goes on in the body, including metabolism of food and drugs, converting food into essential nutrients, and filtering wastes to be excreted out of the body. As such, it is hardly surprising that the liver is the prime target of any type of metastatic cancerous growth.
Liver cancer in dogs may be primary or secondary. Primary liver cancer is the one that originates in the liver itself. Cancer that has originated from elsewhere in the body and metastasized (spread) to the liver is known as secondary liver cancer.
Primary liver cancer is usually the result of exposure to environmental carcinogens (chemicals capable of causing cancer). The liver is responsible for detoxification of the body, and many chemicals turn toxic or increase in toxicity after they have been metabolized by the liver. Food additives and preservatives, pesticides and fungi on spoiled pet food, dyes and certain plants are potential carcinogens that may lead to toxicity and liver cancer in dogs. However, certain viral infections that cause liver cancer in humans have not yet been observed in dogs.
Primary liver cancer is a rare development. Even in cases where it does occur, cancer arises from the liver cells. Liver tumors are not necessarily always malignant. Hepatocellular carcinomas are malignant while hepatocellular adenomas are benign epithelial tumors.
The affect of liver cancer depends not only on the malignancy, but also on the size of the tumor. Benign tumors do not spread or cause any major illness. They cause a problem only if they encroach upon neighboring organs or burst open. Benign liver tumors may sometimes reduce blood sugar levels, as it is suspected that they release substances similar in effect as that of insulin. Therefore, when lower blood sugar levels are also observed, the possibility of pancreatic liver cancer in dogs should first be ruled out, since insulin production for controlling blood sugar levels is controlled by the pancreas.
Primary liver cancer in dogs comprises less than 2% of all types of cancers seen in dogs, and most of the time, it is cancer in another organ of the body that has spread and affected the liver. Similarly, primary liver cancer can spread and affect other organs. Metastatic cancers are mostly malignant in nature and have a poor prognosis.
The liver is the biggest organ in the body, and its importance can be judged by the fact that it has large regenerative cell capacities. The liver is known to remain functional even when more than a third of its mass has been affected by disease. The fact that symptoms of liver cancer like vomiting, abdominal bloating, lethargy, respiratory problems, pale gums and weight loss are vague is another factor that leads to late detection.