Page 605 - Small Animal Internal Medicine, 6th Edition

CHAPTER 35 Hepatobiliary Diseases in the Cat 577

TABLE 35.4 be euthanized on the basis of finding a hepatic mass with no
evidence of metastases on ultrasonography.
VetBooks.ir Primary Liver Tumors in Cats or histopathology; as mentioned earlier, cats with hepatic
A definitive diagnosis is usually obtained using cytology
TYPE OF TUMOR
BEHAVIOR
lymphoma may have ultrasonographically normal-appearing
livers, so FNA should always be performed in these patients.
Bile Duct Tumor In some cases FNA may be diagnostic, but in others they
Biliary carcinoma Most common primary liver may be difficult to interpret, particularly in cats with benign
(including tumor in cats (>50%) hepatocellular tumors, in which the cells are indistinguish-
cystadenocarcinoma) Biliary carcinoma most able from normal hepatocytes. Ultrasonography-guided
Biliary adenoma common malignant feline
Gallbladder tumors liver tumor Tru-Cut–type biopsies are usually diagnostic; alternatively,
Aggressive behavior—diffuse biopsies can be obtained during laparoscopy or laparotomy.
intraperitoneal metastases In the case of an apparently single lesion, the clinician may
in 67%-80% of cases elect to proceed straight to surgical removal and an exci-
sional biopsy. Hemostasis profiles should be evaluated before
Hepatocellular Tumor performing a biopsy. It is unusual for the one-stage pro-
Hepatocellular carcinoma Recognized but less common thrombin time and activated partial thromboplastin time to
(HCC) than biliary tumors be prolonged in cats with primary liver tumors, but they can
Hepatocellular adenoma Adenoma more common be markedly prolonged in cats with diffuse hepatic infiltra-
(hepatoblastoma; very than carcinoma tion with lymphoma or other diffuse secondary tumors (e.g.,
rare) mast cell tumors). Biopsies should not be considered in these
Neuroendocrine Tumor cases until clotting factors have been replenished with a
Hepatic carcinoid Very rare but very aggressive fresh-frozen plasma transfusion.
Primary Hepatic Sarcoma Treatment
Hemangiosarcoma, Uncommon Treatment of primary hepatic tumors relies on surgi-
leiomyosarcoma, others Most locally aggressive, high cal removal if they are resectable. This is advisable even
metastatic rate in cats with benign tumors, including biliary adenomas.
Hemangiosarcoma most Treatment of diffuse, nodular, or metastatic tumors may
common primary hepatic be difficult. Primary hepatic tumors generally have a poor
sarcoma in cats response to chemotherapy. It has been suggested that this
is because hepatocytes, normal and transformed, have
Note: Benign tumors are more common than malignant tumors in
this species. high expression of the multidrug resistance membrane-
associated P-glycoprotein and that hepatocytes are natu-
rally high in detoxifying enzymes. Radiotherapy is not
Radiographs may show hepatomegaly; the liver may have wise because normal liver tissue is very radiosensitive.
an irregular border or focal enlargement of one lobe. There For additional information, please see Chapter 79 (the
may be also involvement of other organs (e.g., lymph- section on lymphoma) and Chapter 81 (the section on mast
adenopathy in cats with lymphoma), and thoracic radio- cell tumors).
graphs may reveal evidence of metastases. However,
radiographs may also be normal. Some malignant hepatic Prognosis
tumors commonly seed the peritoneum and metastasize to The prognosis of benign tumors is good after resection but
local lymph nodes or lungs. As in other diseases of the liver, poor for cats with any type of malignant liver tumor. However,
ultrasonography is more helpful in identifying a hepatic most cats with lymphoma of the liver respond to chemo-
mass and evaluating for metastases; it also allows for FNA of therapy (see Chapter 78).
the mass(es). Hepatic tumors can also be cystic, particularly
cystadenocarcinomas (see Fig. 35.9). Cats, unlike dogs,
rarely have benign nodular hyperplasia in the liver, so this is CONGENITAL PORTOSYSTEMIC SHUNTS
not a likely differential diagnosis for a hepatic mass. Diffuse
hepatic tumors (e.g., lymphoma) may show a diffuse change Etiology and Pathogenesis
in echogenicity, or the liver may appear normal on ultraso- PSSs are abnormal vascular communications between the
nography. Important differential diagnoses for diffuse portal and systemic circulations. They may be congenital or
hepatic tumors are FIP, lipidosis, and amyloidosis. A thor- acquired secondary to portal hypertension. The latter are
ough abdominal ultrasonographic examination should be usually multiple vessels and are very rare in cats because they
undertaken to search for evidence of metastases. It should usually occur secondary to congenital hepatic fibrosis (see
be kept in mind that, because benign tumors are more earlier) and cirrhosis, both uncommon in cats. Acquired PSS
common than malignant tumors in cats, no animal should secondary to a congenital hepatic arteriovenous (AV) fistula