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Carolina da Fonseca Sapin, Cristina Gevehr Fernandes, Márcia de Oliveira Nobre & Fabiane Borelli Grecco
Background: The prevalence of intracranial neoplasms in dogs represents 2.1 to 4.0% of the cases. Brain tumors may be
primary or metastatic. The objective of this study was to describe two cases of intra encephalic neoplasia in elderly dogs
received for necropsy by the Veterinary Oncology Service in the Federal University of Pelotas.
Cases:
Case 1: A 12-year-old female canine, without breed and medium size, was received for necropsy. The animal has
had behavioral changes. Macroscopic examination of the encephalus revealed asymmetry and congestion. The organs were
collected and fixed in 10% formalin. In the brain cleavage we noticed an extensive brown-gray mass with reddish areas,
expansive, moderately demarcated, soft to cut and discrete hydrocephalus. Serial fragments of the brain and fragments
of the organs were sent for processing. The slides were stained with the hematoxylin and eosin technique for histopathological analysis. At the microscopic examination, cuboidal cells were observed in the encephalus sometimes in acinar arrangements, of extensive and very limited pattern, diagnosed as ependymoma. Case 2: It is a 15-year-old, female Poodle
dog, with several tumors. During necropsy multiple subcutaneous nodules, mesentery, intestinal serosa, stomach and liver
were noticed. At the cut these were firm and whitish. No macroscopic changes were observed in the other organs. Fragments of organs and brain were collected and a serial section of the encephalus was performed for further processing and
histological analysis. In the histopathological analysis the masses were constituted by proliferation of sometimes rounded
cells, elongated, with rounded nuclei and eosinophilic cytoplasm, allowing the diagnosis of mesothelioma. The same
cell pattern was observed in other organs. In the frontal cortex of the encephalus there were small foci of cells similar to
those observed in the mesentery, as well as metastatic emboli in the meningeal and encephalic vessels, characterizing the
diagnosis of metastatic mesothelioma.
Discussion: Neoplasms of the central nervous system may be primary or metastatic. The ependymoma observed in case 1
was only diagnosed after visualization of the encephalic mass during necropsy, pointing to the importance of postmortem
examination. Brain neoplasms in dogs occur with a frequency and variety similar to that of humans. Most of these are
found in older dogs, and 95% of those affected are over five years of age. One situation that may occur in ependymomas
is the development of obstructive hydrocephalus by the expansion of the neoplasm into the ventricular system. The animal
studied in case 1 presented behavioral changes for weeks before death, and at necropsy ventricular dilation was evidenced,
suggesting that hydrocephalus had occurred and the behavioral changes due to tumor localization. Metastatic brain neoplasms occur due to the hematogenous spread of many tumors. The species in which the metastatic neoplasms are most
commonly described is the canine. Metastases of mesotheliomas in the central nervous system are rare, which reinforces
the need for a thorough postmortem examination, as evidenced in the second case of this study, since the animal did not
manifest clinically signs of neurological involvement and the metastasis was only identified microscopically by serial cuts
of the encephalon. It can be concluded that detailed, systematic and serial post-mortem examination of the central nervous
system should be part of the diagnostic routine even if no clinical neurological signs are evident. The reports presented
here are of importance since they are considered rare diagnoses of primary and metastatic brain tumors.
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