Page 642 - Small Animal Internal Medicine, 6th Edition

614 PART IV Hepatobiliary and Exocrine Pancreatic Disorders

hepatic tumors seen in dogs and their relative importance cirrhosis or benign nodular hyperplasia, which are also
and metastatic potential are outlined in Table 36.3. common in older dogs. Therefore no dog should be eutha-
VetBooks.ir Clinical Features nized on the basis of a presumptive diagnosis of a liver mass
on clinical examination or diagnostic imaging without sup-
Clinical signs and physical examination findings in dogs
hepatocellular carcinoma, which can occur in three different
with primary or secondary liver tumors are nonspecific, portive histology. The left liver lobes are often affected by
except for diffuse or nodular hepatomegaly. Even this can be patterns—massive (single, large nodule; most common),
confused with other conditions, such as macronodular nodular (multiple smaller nodules), and diffuse (indistinct
nodules throughout). The behavior of each type of tumor
tends also to be different, as outlined in Table 36.3.
TABLE 36.3 Clinicopathologic abnormalities are similarly not specific
for neoplasia, and blood test results may be normal, even in
Primary Liver Tumors in Dogs* dogs with extensive involvement. Dogs with lymphoma infil-
trating the liver usually have marked increases in ALT and
TYPE OF TUMOR COMMENTS ALP activities but are rarely jaundiced; moreover, although
the liver usually looks abnormal on ultrasonography, they
Hepatocellular Tumors may have normal liver echotexture. The authors occasionally
Hepatocellular carcinoma HCC most common primary see dogs with marked hepatic involvement with large cell
(HCC) liver tumor in dogs (50%) lymphoma that have normal liver enzyme activities. Hypo-
Hepatocellular adenoma, Most are massive; some glycemia has been described in association with hepatocel-
hepatoma nodular or diffuse lular carcinoma in dogs and can be caused by paraneoplastic
Hepatoblastoma—very rare Miniature Schnauzers, male production of insulin-like growth factor. Cytology usually
dogs may be at
increased risk allows the distinction of solitary hepatocellular carcinomas
MR, 0%–37% for massive from nodular hyperplasia. Massive forms of hepatocellular
forms, 93%–100% for carcinoma have a low metastatic rate. Metastases from other
nodular and diffuse diffuse and nodular forms of hepatocellular carcinoma or
forms biliary carcinoma usually occur early; the most common
Adenoma uncommon and sites are the liver, regional lymph nodes, lung, and peritoneal
usually incidental surfaces. Hepatocellular adenoma (hepatoma) is a benign
tumor that usually occurs as a single mass that is typically
Biliary Tract Tumors smaller than the massive form of hepatocellular carcinoma
Biliary carcinoma Bile duct carcinomas but can be multifocal. Histologic features of hepatocellular
(including second most common adenoma are similar to those of nodular hyperplasia (or
cystadenocarcinoma) primary tumor in dogs
Biliary adenoma (22%–41% of malignant normal liver), except for the presence of a fine rim of reticu-
Gallbladder tumors canine liver tumors) lin surrounding the adenoma and lack of apparent normal
Labrador Retrievers, architecture—that is, few portal tracts and no central veins.
females may be at
increased risk Treatment and Prognosis
Usually aggressive When a single large hepatic mass is identified, it can be dif-
MR up to 88% ficult to distinguish a well-differentiated hepatocellular
Adenomas uncommon, carcinoma from nodular hyperplasia and hepatocellular
gallbladder tumors very adenoma from ultrasonography, CT imaging, or gross
rare appearance; however, as noted, cytology is usually helpful.
Neuroendocrine Tumor Surgical resection is the treatment of choice for primary
Hepatic carcinoid Very rare, but always hepatic neoplasms and massive hepatocellular carcinoma. In
diffuse or nodular, and the latter, it usually carries a good prognosis provided the
very aggressive tumor can be fully resected because these have a lower meta-
static rate than the more diffuse and nodular forms of the
Primary Hepatic Sarcomas tumor, and the local recurrence rate after liver lobectomy is
Hemangiosarcoma, Uncommon reportedly less than 13%. Long-term (2- to 3-year) survival
leiomyosarcoma, Most locally aggressive, rates after surgical resection are common in dogs with
gastrointestinal stromal diffuse, or nodular; high massive hepatocellular carcinoma. Surgical excision is there-
tumors, others MR fore the treatment of choice for single tumors involving one
liver lobe because this allows diagnosis and, in many cases,
MR, Metastatic rate.
*Note that malignant tumors are more common than benign tumors cure.
and that metastases to the liver are more common than primary The prognosis for diffuse and nodular hepatocellular car-
liver tumors in dogs. cinomas and other forms of primary malignant liver tumors