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Meningioma with rhabdoid features: Pathologic findings in dogs
Alexandru-Flaviu Tabaran1,2, Anibal G Armien1,3, G Elizabeth Pluhar1
1University of Minnesota, St. Paul, MN.
Abstract:
Rhabdoid meningioma is a rare type of meningeal neoplasm in humans. This study reports the clinical, pathological, and ultrastructural features of 4 cases of canine meningioma with rhabdoid features. The cases were female and 8 to 12 years of age. Biopsies from complete surgical resections were examined for all cases. The whole brain with tumor recurrence was collected at necropsy in 2 dogs. Histologically, the tumors consisted of discohesive sheets of oval-polygonal cells with abundant eosinophilic cytoplasm and occasional paranuclear hyaline-like inclusions. Cells were intensely immunopositive for vimentin, negative for melan A and S100 protein in all cases, and showed variable immunolabeling for cytokeratin in 2 cases. Focal glial fibrillary acidic protein (GFAP)-immunopositive cells were present in 1 case. Ultrastructurally, the rhabdoid cells in case 1 contained prominent cytoplasmic whorls of intermediate filaments, recapitulating the ultrastructural features of rhabdoid meningioma in humans. In cases 2 and 3, the meningioma cells contained interdigitating cell processes folded in a maze-like fashion resembling rhabdoid-like meningioma in humans. In case 4, the voluminous cytoplasm contained many round-to-flattened mitochondria admixed with rough endoplasmic reticulum, indicating a predominant oncocytic differentiation and not the rhabdoid differentiation suggested by light microscopy. Thus, rhabdoid morphology occurs in different types of meningiomas, and ultrastructural findings are essential for a correct diagnosis.
Insights
Canine meningiomas can exhibit rhabdoid morphology, mimicking human tumors. Ultrastructural analysis is crucial for accurate diagnosis, revealing diverse cellular differentiations beyond rhabdoid features.
Area of Science:
- Veterinary Pathology
- Comparative Oncology
- Neoplasia
Background:
- Rhabdoid meningioma is a rare human meningeal neoplasm.
- Canine meningiomas are common intracranial tumors, but rhabdoid variants are poorly characterized.
- This study investigates canine meningiomas with rhabdoid features.
Purpose of the Study:
- To describe the clinical, pathological, and ultrastructural characteristics of canine meningiomas with rhabdoid features.
- To compare these findings with human rhabdoid meningiomas.
- To determine the diagnostic utility of ultrastructural examination in these cases.
Main Methods:
- Histopathological examination of tumor biopsies from 4 canine cases.
- Immunohistochemical analysis for vimentin, melan A, S100 protein, cytokeratin, and glial fibrillary acidic protein (GFAP).
- Ultrastructural evaluation using transmission electron microscopy.
Main Results:
- Tumors consisted of discohesive cells with eosinophilic cytoplasm and hyaline-like inclusions.
- Immunohistochemistry showed vimentin positivity in all cases, variable cytokeratin, and focal GFAP positivity in one case.
- Ultrastructural findings varied: prominent intermediate filament whorls in one case, maze-like cell processes in two, and oncocytic differentiation in one, challenging the initial rhabdoid diagnosis.
Conclusions:
- Rhabdoid morphology in canine meningiomas can arise from different tumor types.
- Ultrastructural examination is essential for differentiating true rhabdoid meningioma from other neoplasms with similar light microscopic appearances.
- These findings aid in comparative pathology and understanding meningioma heterogeneity.
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