Page 1366 - Clinical Small Animal Internal Medicine

1304 Section 11 Oncologic Disease

biliary cystadenomas or hepatobiliary cystoadenomas. due to their aggressive clinical course and high rate
VetBooks.ir These are considered benign tumors and are the most of metastasis. Metastasis to the lungs and spleen is
most common and is reported in 86–100% of cases.
common hepatobiliary tumor found in the cat (account­
ing for 50% of all feline hepatobiliary tumors). Similar to
tumors are massive and 64% are nodular. Bear in mind
hepatocellular adenomas, biliary adenomas typically do Morphologically, approximately 36% of mesenchymal
not cause clinical signs in affected patients unless they that the liver is also a common site for secondary
reach a large enough size to cause abdominal discomfort, sarcomas including metastatic hemangiosarcoma and
necessitating surgical removal. Male cats are thought to disseminated histiocytic sarcoma.
be overrepresented.
Bile duct carcinomas (also called cholangiocarcino­
mas) are malignant tumors in both dogs and cats. They Epidemiology
have an aggressive clinical course with metastasis
detected in 60–80% of affected patients. Metastasis to As discussed earlier, liver tumors in the dog and cat can
the local lymph nodes and lungs is most common but be of either primary or secondary origin. In the dog, ret­
other intraabdominal sites have been reported. In cats, rospective studies have indicated that the prevalence of
metastasis resulting in diffuse carcinomatosis can occur primary hepatic neoplasia is low (0.6–1.5% of all canine
in 67–80% of cases. Bile duct carcinomas can be intrahe­ tumors). Secondary neoplasia, the result of metastasis to
patic, extrahepatic, or occasionally within the gallblad­ the liver, is a much more common occurrence. Tumors
der itself. Morphologically, bile duct carcinomas are originating in the spleen, pancreas, and gastrointestinal
similar to HCC in that 37–46% are massive, 0–46% are tract are the most likely to result in metastasis to the
nodular and 17–54% are diffuse. In dogs, females and liver. However, other systemic neoplasms such as lym­
Labrador retrievers are thought to be predisposed phosarcoma, malignant histiocytosis or systemic masto­
whereas there is no sex or breed predisposition yet cytosis often involve the liver as part of their widespread
confirmed in cats. clinical course.
In cats, the prevalence is similar, with 1.0–2.9% of all
Neuroendocrine Tumors feline tumors being of primary hepatic origin. However,
when one study excluded hematopoietic neoplasms, the
These tumors arise from the neuroectodermal cells. prevalence increased to 6.9%. There are currently no
They are considered rare tumors in both the dog and cat studies documenting the frequency of metastatic disease
and are often referred to as carcinoids. Carcinoids have to the liver in cats.
a tendency to occur in younger animals compared to
other hepatobiliary tumors. They have an aggressive
clinical course and carry a poor prognosis, primarily
due to the fact that early metastasis is found in >90% of Signalment
patients diagnosed. The most common sites of metasta­
sis were the peritoneum and lymph nodes. These Hepatobiliary tumors are most common in older animals
tumors are typically intrahepatic and have a predilec­ (over the age of 10), the exception to this being carci­
tion for a nodular or diffuse presentation, making noids which are typically found in younger animals (71%
surgical resection often difficult or impossible. A small of dogs were under the age of 10). Some studies indicate
number of extrahepatic neuroendocrine tumors of the that miniature schnauzers may be overrepresented
gallbladder have been reported for which surgical for the development of HCC and Labrador retrievers
resection was performed but long‐term follow‐up is may be predisposed to bile duct carcinomas but there are
unavailable. no other known breed propensities in either species.
One study documented a male predilection for canine
HCC and a female predilection for bile duct carcinoma.
Mesenchymal Tumors (Sarcomas) In cats, some studies have indicated a male predomi­
Mesenchymal tumors, also called sarcomas, arise from nance for carcinoids and bile duct tumors.
the stromal cells of the liver. They are considered rare,
making up less than 15% of all primary hepatic tumors.
There are several different subtypes of sarcomas that History and Clinical Signs
have been reported in the canine and feline liver
including hemangiosarcoma (most common in the dog), In dogs with hepatobiliary tumors, clinical signs are often
leiomyosarcoma (most common in the cat), fibrosar­ lacking or will be somewhat vague. These may include
coma, osteosarcoma, rhabdomyosarcoma, and liposar­ things such as anorexia, weight loss, lethargy, and vomit­
coma. Primary hepatic sarcomas carry a poor prognosis ing. Less frequently, symptoms such as abdominal