Hepatic neoplasia is cancer of the liver. 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

Vomiting

Decreased appetite

Abdominal distension

Pale gums

Generalized weakness

Increased respiratory rate

Difficulty breathing

Jaundice (yellow discoloration of the skin)

Weight loss