Primary hepatic and biliary tract tumors in dogs and cats: An overview - Veterinary Medicine
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Primary hepatic and biliary tract tumors in dogs and cats: An overview
Since many of the clinical signs of hepatobiliary tumors are nonspecific, these tumors may be advanced at diagnosis. However, using the correct diagnostic tools, including cytology, tissue biopsy, and abdominal imaging, may lead to an earlier diagnosis and a better outcome.


VETERINARY MEDICINE


Canine hepatocellular carcinoma


Table 2 Characteristics of Selected Hepatobiliary Tumors
Canine hepatocellular carcinoma accounts for more than 50% of all primary hepatobiliary tumors (Table 2).29 The average age of affected dogs is 11 or 12 years, with more than 80% of dogs being 10 years or older.4,21,29 Although most studies have not found a breed predisposition, 16% of the affected dogs in one report were schnauzers.4,21,29

Diagnosis


Table 3 Selected Clinical Features of Primary Canine Hepatobiliary Tumors
Abdominal palpation may reveal hepatomegaly or a hepatic mass in about 50% of patients (Table 3).21,22 Clinical signs include weight loss, polyuria, polydipsia, vomiting, anorexia, lethargy, and, less commonly, ascites, seizures, diarrhea, and abdominal pain.21,22,29 Seizures are usually attributed to hepatic encephalopathy or hypoglycemia and, less likely, to brain metastasis.29,30


Hepatobiliary tumors in people
Although many dogs with hepatocellular carcinoma present for evaluation of obvious clinical signs of illness, nearly one-third of dogs are asymptomatic, with the discovery of hepatocellular carcinoma being an incidental finding.21,22 Nonspecific hematologic abnormalities are common and may include mild to moderate anemia and leukocytosis.21,22,29 Most affected dogs have elevations in liver enzyme activities, including ALT, aspartate aminotransferase (AST), and ALP; however, hyperbilirubinemia is present in only 20% to 38% of patients.1,21,22,29 Hypoglycemia can be associated with hepatocellular carcinoma; however, documentation of a low blood glucose concentration is relatively rare (less than 5%) in dogs without any overt clinical signs.22 Despite the low frequency of hypoglycemia in asymptomatic dogs, hepatocellular carcinoma should remain a top differential diagnosis in dogs with known hepatic neoplasia and clinical signs of hypoglycemia.30 Furthermore, in dogs with extensive or advanced hepatocellular carcinoma, hepatic function may be markedly compromised, resulting in prolonged coagulation times in up to 21% of patients.21,22 To minimize the likelihood of excessive and life-threatening hemorrhage in these patients, consider the possibility of altered hemostasis before biopsy or surgical intervention. In patients at risk for excessive hemorrhage, consider fine-needle aspiration and cytology as a less invasive option than liver biopsy for obtaining a definitive diagnosis of hepatocellular carcinoma.

Classification

Most canine hepatocellular carcinomas arise from the left side of the liver, particularly the left lateral lobe.4,17,22,29 Traditionally, hepatocellular carcinoma in dogs may be classified as one of three forms: massive, nodular, or diffuse. More than 50% of hepatocellular carcinomas are massive, usually presenting as a solitary mass involving one liver lobe.29 The reported frequency of adjacent liver lobe involvement in dogs with massive hepatocellular carcinoma is variable. Although previous reports demonstrated additional liver lobe involvement in 20% to 80% of dogs at necropsy, more recent work involving 42 dogs undergoing surgical excision for massive hepatocellular carcinoma found no evidence of additional masses in any patient.1,22,29 Similarly, previous postmortem studies reported a 22% to 36% distant metastatic rate (lymph nodes, peritoneum, lungs), while more recent studies report less than 5% metastasis at diagnosis.1,22,29 The discrepancy between the presence of metastases at diagnosis vs. at necropsy would suggest that early detection and surgical intervention may result in a longer local disease-free interval and may reduce the risk of metastatic dissemination.

The nodular form of hepatocellular carcinoma is characterized by nodules in multiple liver lobes and accounts for 16% to 29% of canine hepatocellular carcinoma cases, while the diffuse form accounts for only 10% of cases. Early reports demonstrated an extremely high metastatic rate (93% to 100%) for these forms of canine hepatocellular carcinoma.1,29 However, the reported metastatic rate, surgical inoperability, and suspected overall poor prognosis are based on necropsy findings, and earlier clinical detection may result in a better outcome.


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