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.


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Treatment

While there is an apparent lack of good treatment options for nodular or diffuse hepatocellular carcinoma, massive hepatocellular carcinoma can often be treated effectively with excisional surgery. However, because of the anatomical location and proximity to large blood vessels, the intraoperative mortality rate approaches 5% in dogs surgically treated for massive hepatocellular carcinoma.22 Overall, survival times for dogs treated surgically are generally favorable, with many patients achieving long survival times. In one study, more than 50% of dogs surgically treated for massive hepatocellular carcinoma were alive one year after surgery (range = one day to greater than 1,025 days).21 In another study, dogs treated with surgical excision had a longer median survival time (> 1,460 days, mean 409 days) than those treated with conservative medical management only (median survival time 270 days, mean 162 days) had.22

Although surgery is considered the best treatment for massive hepatocellular carcinoma, postoperative survival times may be dictated by primary tumor location since patients with neoplasms resected from the left, central, or right liver lobes appear to have differing median survival times—1,460+, 795+, or 365 days, respectively.22 The difference in median survival times is likely due to variables including the difficulty of the surgical approach and the tumor's proximity to vasculature.

Canine biliary carcinoma

Biliary carcinomas include biliary cystadenocarcinomas and, rarely, carcinomas of the gallbladder. These tumors account for 21.8% of primary hepatobiliary tumors (Table 2).31 The average age of affected dogs is 10 to 11.4 years; almost two-thirds of the dogs are more than 10 years old.4,17,32 Females are overrepresented in multiple studies, and one report suggested an increased risk for biliary tumors in Labrador retrievers, as well as spayed dogs compared with intact females.33

More than half of the affected dogs have palpable hepatomegaly or a mass (Table 3), and icterus is apparent in up to 23% of the affected dogs.1,31 The clinical signs are comparable to those seen with other hepatobiliary tumors, although vomiting may be less common.4 Trends in biochemical findings conflict among studies; however, elevations in ALT and ALP activities and bilirubin concentrations may be seen.1,4

The malignant transformation of biliary epithelium more commonly occurs within the hepatic parenchyma, and it has been reported that the development of intrahepatic tumors is three times as likely as the development of extrahepatic tumors.33 Necropsies have shown that biliary carcinomas tend to possess an aggressive phenotype, capable of spreading to adjacent liver lobes, regional lymph nodes, and distant sites in dogs.1,33,34 While the pathogenesis for biliary carcinoma in dogs remains poorly defined, chronic inflammation may be involved, as suggested by the association of carcinoma development and concurrent parasitic infestations.33,34

Similar to hepatocellular carcinomas, biliary carcinomas tend to affect the left lateral liver lobe in most patients, and about 50% of biliary carcinomas are solitary lesions (massive form).1,4,17,31 When anatomically feasible, these tumors are typically treated with surgical excision. Negative prognostic factors established in a recent evaluation of dogs undergoing surgery for extrahepatic biliary tract neoplasia included septic bile peritonitis, an elevated creatinine concentration, and an elevated partial thromboplastin time.35


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