Meningiomas in dogs: clinical, histopathological and immunohistochemical aspects

Abstract:

Neoplasias of the central nervous system (CNS) of small animals are frequently diagnosed; however, data relative to prevalence are scarce. The aim of this study was to evaluate retrospectively the occurrence of primary CNS tumors in dogs in a Veterinary Teaching Hospital and describe clinical, histopathological and immunohistochemical aspects of the most common tumors. Fourteen cases of CNS primary neoplasia (prevalence of 0.27%) were identified from 1998 to 2013; from these 11 were diagnosed as meningiomas. The mean age of dogs with meningiomas was 10 years; male (7/11) and the Boxer breed (3/11) were most commonly represented. Seven meningiomas were located in the spinal cord and four intracranially; the main clinical signs were impaired locomotion and seizures, respectively. Pulmonary metastasis was found in two cases. Myelography was performed in six dogs with spinal meningiomas. In these cases it was effective in demonstrating the deviation or interruption of the contrast column. Exploratory surgery to confirm diagnosis or remove the tumor was performed in five animals and the survival rate varies 85 to 960 days. Meningiomas were histologically classified as transitional (4/11), meningothelial (2/11), papillary (2/11), angiomatous (1/11), microcystic (1/11) and anaplastic (1/11). Evaluation of histological grade was performed; 10 meningiomas were classified as grade I and one as grade III. The neoplastic cells of eight tumors (8/11) were positive for Masson's trichrome and one with the Congo red histochemical techniques. The immunohistochemical assays revealed in all tumors a positive immunoreactivity for vimentin but negative staining for factor VIII and p53. Immunolabelling for S100 (6/11), GFAP (5/11) and pancytokeratin (3/11) showed a variable staining intensity. The mean cell proliferation index was 3.2 mitotic figures and 3.4% for Ki-67 immunostaining. The results confirmed that meningiomas are the most frequent primary CNS neoplasia in dogs, with variation in histological subtypes. Histochemical and immunohistochemical characterization contributed to the diagnosis; however, studies of the expression of other genes are necessary to assist with the prognosis of this kind of neoplasia.

Index Terms:
Neoplasms; meningiomas; central nervous system; immunohistochemistry; dogs