Encephalic meningioangiomatosis in a cat.

Meningioangiomatosis (MA) is a rare proliferative meningovascular entity that has been described mainly in humans and dogs. Here we describe MA in a 13-y-old spayed female domestic shorthaired cat that died 5 d after acute change in behavior, open-mouth breathing, seizures, hyperthermia, and inability to walk. On MRI, the lesion appeared predominantly as extraparenchymal hemorrhage. Autopsy changes consisted of a dark-red, hemorrhagic plaque that expanded the leptomeninges and outer neuroparenchyma of the right piriform and temporal telencephalic lobes, chalky white nodules in the peripancreatic fat, and yellow fluid in the abdomen. Histologically, the lesion in the brain consisted of leptomeningeal thickening by spindle cells that effaced the subarachnoid spaces and extended perivascularly into the underlying cerebral cortex. Spindle cells were arranged as streams or whorls around blood vessels, and had slender eosinophilic cytoplasm and elongated nuclei with coarsely stippled chromatin and 1 or 2 distinct nucleoli. There was extensive hemorrhage, clusters of hemosiderin-laden macrophages, and mineralization throughout. Spindle cells had positive immunolabeling for vimentin. A striking MRI and gross feature in our case was the extensive hemorrhage associated with the MA lesion. Additional findings included suppurative pancreatitis with peritonitis and supraspinatus myonecrosis.