Page 680 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

658 PART IV Specific Malignancies in the Small Animal Patient

TABLE 31.1 World Health Organization Classification and Frequency of Primary Brain Tumors in Dogs and Cats
a
VetBooks.ir Tissue of Origin Tumor Types/Grades Canine Frequency of Tumor Diagnosis 3,5,6,21–23
Feline
1,2,5–7,20,21,24,25
Meninges
• Grade I
Meningioma 42%–52% 40%–59%
• Grade II (atypical)
• Grade III (malignant)
Neuroepithelium Astrocytic tumors 13%–60% <1%–3%
• Grade I (pilocytic)
• Grade II (diffuse)
• Grade III (anaplastic)
• Grade IV (glioblastoma)
Oligodendroglial tumors 1%–23% <1%–3%
• Grade II (oligodendroglioma)
• Grade III (anaplastic)
Oligoastrocytic tumors <5% NA
• Grade II (oligoastrocytoma)
• Grade III (anaplastic)
Choroid plexus tumors 5%–8% <1%
• Grade I (papilloma)
• Grade II (atypical papilloma)
• Grade III (carcinoma)
Embryonal tumors <0.5% <1%
• Primitive neuroectodermal tumor (Grade IV)
Ependymoma 0.2%–6% 3%
• Grade II (ependymoma)
• Grade III (anaplastic)
a Frequency of diagnosis among all primary brain tumors.
NA, data not available.

canine intracranial tumors, with hemangiosarcoma (HSA, 29%– the region revealing single nucleotide variants in three neighbor-
35%), pituitary tumors (11%–25%), lymphoma (12%–20%), ing genes DENR, CAMKK2, and P2RX7 that are highly associ-
23
and metastatic carcinomas (11%–20%) accounting for 77% to ated with glioma susceptibility. The CAMKK2 and P2RX7 genes
86% of all SBTs. 1,4 have been previously recognized as relevant to the development or
23
Brain tumors in dogs may occur at any age and in any breed progression of human cancers.
with no reported sex predispositions. Most PBTs and SBTs occur
in middle-aged to older dogs, with the majority of cases described Cats
being greater than 5 years of age. Pooled data from the most cur-
rent retrospective studies indicate that the median ages at diag- Intracranial tumors are less common in cats compared with dogs.
nosis for dogs with meningiomas, gliomas, and CPTs were 10.5 Approximately 70% of all feline intracranial tumors are PBTs
years, 8.0 years, and 5.5 years, respectively. 1,2,20,21 There is a pro- and more than 50% of PBTs in cats are meningiomas. 3,6,15 Other
pensity for PBTs in juvenile animals to be neuroepithelial tumors types of PBTs, such as ependymomas, gliomas, and choroid plexus
of glial, neuronal, or embryonal origin. 1,22 One study identified a tumors, are infrequently reported (see Table 31.1). 3,6,15 The most
significant linear relationship between age and body weight and common SBTs in cats are lymphoma and pituitary tumors, which
the occurrence of PBTs; large-breed dogs were at significantly accounted for nearly 50% and 30%, respectively, of all feline SBTs
increased risk for developing meningiomas and CPTs. Golden in one study. The median age at diagnosis of cats with menin-
3
1
retrievers, boxers, miniature schnauzers, and rat terriers have gioma is 11 years, whereas neuroepithelial tumors and lymphoma
been identified as breeds in which intracranial meningiomas are are typically seen in cats in the 7- to 8-year age range. 3,24 There
overrepresented. 1,2,19,20 are no known breed or sex predilections for cats to develop brain
Although CPTs were overrepresented in golden retrievers in tumors.
21
one report, this breed predisposition was not corroborated in a
1
subsequent investigation. Gliomas (astrocytomas and oligoden- Pathophysiology, History, and Clinical Signs
drogliomas) are highly overrepresented in brachycephalic breeds
including boxers, Boston terrier, bullmastiffs, and English and PBTs and SBTs are space-occupying intracranial lesions that cause
1,2
French bulldogs. A recent study has also identified a locus on clinical signs of brain dysfunction by directly compressing or invad-
canine chromosome (CFA) 26 that is strongly associated with ing brain tissue and indirectly through secondary effects, such as
glioma across multiple dog breeds, with subsequent mapping of induction of peritumoral edema, neuroinflammation, obstructive