Page 478 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

456 PART IV Specific Malignancies in the Small Animal Patient

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• Fig. 23.20 Intraoperative image of a bile duct cystadenoma in a cat. Sur-
gical resection was curative in this cat.

unlikely to be a major contributor because bile duct carcinomas • Fig. 23.21 Lung metastasis in the cat with bile duct carcinoma depicted
also occur in geographic regions outside the normal distribution in Fig. 23.18. This cat also had diffuse peritoneal metastasis.
of trematodes. 356,360,365
A predilection for Labrador retrievers has been proposed. 365
A sex predisposition has been reported for female dogs. 357,364,372 Sarcomas
In cats, however, the sex predisposition is conflicting. 358–360 The
distribution of morphologic types of bile duct carcinoma is simi- Primary and nonhematopoietic hepatic sarcomas are rare in
lar to HCC, with 37% to 46% massive, up to 54% nodular (see cats and dogs. 354,357–360,380 The most common primary hepatic
Fig. 23.18), and 17% to 54% diffuse. 354,357,364,365 Bile duct carci- sarcomas are hemangiosarcoma (HSA), leiomyosarcoma, and
nomas can be intrahepatic, extrahepatic, or within the gall blad- fibrosarcoma, with HSA the most frequently diagnosed primary
der. 354,357–360,364,365 Intrahepatic carcinomas are more common hepatic sarcoma in cats and leiomyosarcoma the most common
in dogs, 357,364,365 whereas an equal distribution of intrahepatic in dogs. 354,357–360,380,382–385 The liver is a common site for meta-
and extrahepatic tumors to extrahepatic predominance has been static HSA in dogs, whereas only 4% to 6% of HSA occur pri-
reported in cats. 358–360 Solid and cystic (or cystadenocarcinoma) marily in the liver. 384,385 Other primary hepatic sarcomas include
bile duct carcinomas have been reported, but this distinction does rhabdomyosarcoma, liposarcoma, OSA, and malignant mesen-
not influence either treatment or prognosis. 364 Bile duct carci- chymoma. 354–360 The liver, with lungs, LNs, spleen, and bone
noma of the gall bladder is rare in both species. 354,357–360,364,365 marrow, is commonly involved in dogs with disseminated his-
Bile duct carcinomas have an aggressive biologic behavior. tiocytic sarcoma (HS). 386,387 Benign mesenchymal tumors such
Metastasis is common in dogs, with up to 88% metastasizing as hemangiomas are rare. 354–360 There are no known breed pre-
to the regional LNs and lungs (Fig. 23.21); other sites include dispositions, although a male predilection has been reported. 357
the heart, spleen, adrenal glands, pancreas, kidneys, and spinal Diffuse morphology has not been reported, with massive and
cord. 354,357,364,365 In cats, diffuse intraperitoneal metastasis and nodular types accounting for 36% and 64% of sarcomas, respec-
carcinomatosis occur in 67% to 80% of cases. 358–360 tively. 357,380 Hepatic sarcomas have an aggressive biologic behav-
ior, with metastasis to the spleen and lungs reported in 86% to
Neuroendocrine Tumors 100% of dogs. 357,380
Neuroendocrine tumors, also known as carcinoids, are rare in cats Other Primary Hepatic Tumors
and dogs. 354,357–360,367,368 These tumors arise from neuroectoder-
mal cells and are histologically differentiated from carcinomas Myelolipoma is a benign hepatobiliary tumor in cats. 355,356 His-
with the use of silver stains. 355,366 Neuroendocrine hepatobiliary tologically, myelolipomas are composed of well-differentiated adi-
tumors are usually intrahepatic, although extrahepatic tumors pose tissue intermixed with normal hematopoietic elements. 356
have been reported in the gall bladder. 366,377,378,381 Carcinoids Chronic hypoxia has been proposed as an etiologic factor because
tend to occur at a younger age than other primary hepatobi- myelolipomas have been reported in liver lobes entrapped in
liary tumors. 357,366 Morphologically, carcinoids are nodular in diaphragmatic herniae. 356 Myelolipomas can be either single or
33% and diffuse in the remaining 67% of cases. 357,366 Primary multifocal. 356
hepatic neuroendocrine tumors have an aggressive biologic behav-
ior with frequent involvement of more than one liver lobe and History and Clinical Signs
metastasis to the regional LNs, peritoneum, and lungs in cats and
dogs. 357,366,381 Other metastatic sites include the heart, spleen, Hepatobiliary tumors are symptomatic in approximately 50%
kidneys, adrenal glands, and pancreas. 366 of cats and 75% of dogs, especially in animals with malignant