Page 482 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

460 PART IV Specific Malignancies in the Small Animal Patient

have shown some promise with sarcomas in other locations and cat submissions to the Veterinary Medical Database found 8%
warrant consideration for cats and dogs with primary hepatic to relate to cancer and less than 1% (13% of the cancer cases)
Regarding specific tumor types,
438
430,431
to be intestinal neoplasia.
sarcomas.

VetBooks.ir lymphoma comprises nearly 30% of all feline tumors and 6%
of all canine tumors and is the most common intestinal tumor
Other Primary Hepatic Tumors
in most reports. 434,439–441 In 163 cases of feline lymphoma,
Surgical resection with liver lobectomy is recommended for cats the intestine was the most commonly affected site. 442 Adeno-
with primary hepatic myelolipoma, and the prognosis is excellent carcinoma is the second most frequent tumor in both species,
with prolonged survival time and no reports of local recurrence. 356 with mast cell tumors (MCTs) in cats and leiomyosarcomas or
gastrointestinal stromal tumors (GISTs) in dogs the third most
Comparative Aspects common tumors.
As with many cancers, the incidence of intestinal neoplasia
HCC is one of the most common malignancies in humans as a increases in older dogs and cats. Mean ages of affected cats for
result of viral infections with hepatitis viruses B and C and cir- small and large intestinal neoplasia generally range between 10
rhosis induced by alcohol consumption and other disease. 370 A and 12 years, and increasing risk after 7 years of age has been
number of paraneoplastic syndromes have been described includ- reported. 434,438,442–448 Dogs are also usually middle aged or older,
ing hypoglycemia, erythrocytosis, and hypercalcemia. 368 US is with mean ages most often between 6 and 9 years and possibly
considered a good screening imaging modality, but advanced older (12 years) for dogs with leiomyosarcoma. 443,448–452
imaging with contrast-enhanced CT or MRI is preferred to Overall, there may be a slight sex predilection for males to
determine the location, size, and extent of hepatic lesions. 368 develop intestinal tumors. Many studies report a near equal
Other tests include serum α-fetoprotein, serologic tests for hepa- incidence among male and female dogs, 452–455 although one
titis B and C viruses, and histologic confirmation with core liver study did find 76% of dogs with intestinal adenocarcinoma
biopsies. 368 Unlike HCC in dogs, the morphology of HCC to be male. 456 Males also appear overrepresented for smooth
in humans is often nodular or diffuse, which makes definitive muscle tumors, 448 comprising 82% of gastrointestinal (GI)
treatment more problematic. Treatment options depend on the leiomyomas 457 and 76% of dogs with leiomyosarcoma. 451 In
stage of disease and include surgery (e.g., liver lobectomy and addition, 90% of dogs with GI lymphoma were male 448 and
liver transplantation), local ablative therapies (e.g., cryosurgery, there was a slight male predominance in nonlymphomatous
ethanol or acetic acid injection, and microwave or radiofrequency tumors. 441,458,459 In cats, males have greater representation in
ablation), regional therapies (e.g., transarterial chemotherapy, some studies, 446,460 while only slightly exceeding or equaling
embolization, chemoembolization, or RT), and systemic treat- females in other studies. 445,446,460–462
ment with chemotherapy or immunotherapy. 368 Response rates Siamese cats are 1.8 times more likely to develop intestinal neo-
to single- and multiple-agent chemotherapy protocols are less plasia 438 and are overrepresented in studies of intestinal adenocarci-
than 25%, and chemotherapy is no longer recommended for noma, up to eight times greater than other breeds. 434,438,444,458,461
human patients with HCC. 370 Although small numbers of Siamese cats are included in many
Bile duct carcinomas are rare and, similar to those in cats series of feline intestinal lymphoma, one study did show a sig-
and dogs, often associated with a poor prognosis. 382 Risk factors nificant overrepresentation. 443 Otherwise, there is no breed pre-
include primary sclerosing cholangitis, the liver flukes Opisthor- dilection for intestinal lymphoma in cats. In dogs, few studies of
chis viverrini and Clonorchis sinensis in endemic areas of Southeast intestinal neoplasia report an overrepresentation of specific breeds.
Asia and China, and cholelithiasis. 382 Surgical resection is pre- Large-breed dogs in general constituted most cases in a series of
ferred but, because of the high rate of local or regional recurrence, smooth muscle tumors. 454 Collies and German shepherd dogs are
adjuvant treatment with RT or chemotherapy is recommended. 382 overrepresented in some reports for intestinal tumors, especially
However, because of the rarity of this tumor, studies supporting adenocarcinoma, rectal carcinoma, and rectal polyps. 449,463 In a
the efficacy of these adjuvant treatments are lacking. Papillary his- recent Czech necropsy study, breed predispositions were identified
tology, extrahepatic location, and complete resection are favorable in the pug, Leonberger, and English setter for intestinal adenoma;
prognostic factors in humans with bile duct carcinomas. 432 in the English setter and Hovawart for intestinal adenocarcinoma;
and the Doberman and Hovawart for intestinal lymphoma. 448
MCTs have been reported primarily in Maltese. Although these
SECTION G: INTESTINAL TUMORS reports came from Japan, where small breeds are popular, more
than 50% of reported cases in two series were in Maltese dogs with
a male predominance. 464,465
LAURA E. SELMIC, KIM A. SELTING AND With the exception of retroviral influence on the development
JENNIFER K. REAGAN of feline lymphoma, there are no known etiologic organisms or
chemical agents that reliably contribute to the development of
Incidence and Risk Factors spontaneously occurring intestinal neoplasia in dogs and cats.
A recent retrospective study in 55 cats with intestinal carcinoma
Intestinal tumors are rare in dogs and cats. 433–435 In a survey showed significant association between the presence of Helicobacter
of insured dogs in the United Kingdom, a standardized inci- species and development of poorly differentiated large intestinal
dence rate of 210/100,000 dogs was reported for alimentary mucinous adenocarcinoma. 466 The findings of this study suggest
tumors and this accounted for 8% of all tumor submissions. 436 Helicobacter spp. may play a possible role in intestinal carcinoma
Incidence of feline digestive neoplasia in a South African sur- formation and determining site of development in cats. 466 How-
vey comprised 13.5% of all tumors, which likely included oral ever, it has also been suggested Helicobacter species in the feces
tumors. 437 In the United States, a query of more than 300,000 may represent normal flora rather than pathogens. 467