EXPRESS: Meningiomas in four cats with pseudocystic fluid accumulation including one microcystic meningioma.

Case series summaryFour cats were presented with progressive prosencephalic signs. An extraaxial mass associated with a pseudocystic component was identified in each case on MRI and pseudocystic meningiomas were suspected. The appearance of the fluid accumulation in Case 1 was more suggestive of an actual cyst, whereas the crescent shaped fluid accumulation was more compatible with subdural fluid accumulation in Cases 2,3 and 4. All cases underwent mass removal through craniotomy and were discharged from the hospital.The meningiomas were classified as fibrous in case 1,2 and 4, and as microcystic in case 3. The fluid analysis in Case 4 revealed a protein rich fluid with neoplastic meningeal cells. Histology of the wall surrounding the fluid in case 4 revealed tumoral meningothelial cells lined against dura mater, without epithelial lining.All cats improved neurologically after surgical removal of the tumour. Follow-up MRI in cases 2 and 3 performed 6 months post operatively identified focal thickening of the meninges in the two cases (2 and 3).Relevance and novel informationThis case series describes four cats with brain meningiomas associated with a pseudocystic component of unknown origin. Including one microcystic meningioma which has not been previously reported in the veterinary literature. The pseudocyst didn't seem to affect the clinical outcomes and postoperative MRI for these four cats.