JPC SYSTEMIC PATHOLOGY
Signalment (JPC 1777435): Bear
HISTORY: This bear had a one-year history of seizures uncontrollable with antiepileptics.
HISTOPATHOLOGIC DESCRIPTION: Cerebrum: Subjacent to the ependyma, expanding, compressing, replacing portions of the gray and white matter, and extending to cut borders is a well demarcated mass composed of coalescing granulomas up to 2.0 mm in diameter. Granulomas are characterized by numerous acicular clefts (cholesterol clefts) which contain small amounts of amphophilic crystalline debris, surrounded by many multinucleate giant cells (Langhans, foreign body, and touton type), few gitter cells, hemosiderin-laden macrophages, lymphocytes, plasma cells, neutrophils, fibrin, hemorrhage and a small amount of fibrous connective tissue (fibrosis). The adjacent neuropil is multifocally vacuolated (spongiosis) and there is mild microgliosis.
MORPHOLOGIC DIAGNOSIS: Cerebrum: Cholesterol granulomas, multiple and coalescing, bear, ursid.
SYNONYMS: Cholesteatoma, cholesteatosis
· Choroid plexus cholesterol granulomas are common, often incidental findings in mature and aged horses, with an incidence of 15-20% and are rare in other species
· Usually benign with minimal destruction of adjacent tissue
· Believed to develop in choroid plexus stroma as a result of chronic, repeated congestion, edema, and hemorrhage; this results in swelling of the plexus and interstitial tissues, and deposition of cholesterol crystals from degenerate erythrocytes; the cholesterol crystals then act as foreign bodies and elicit a foreign body inflammatory response
TYPICAL CLINICAL FINDINGS:
· Commonly this condition is asymptomatic
· Large masses that compress and destroy cerebral tissue will present with seizures, aggression, dullness, ataxia, and circling
TYPICAL GROSS FINDINGS:
· Firm, crumbly, yellow and soft nodular thickenings of choroid plexus; glistening, pearly appearance on cut surface; expression of white crystals with squeezing of cut surface
· More frequently found in the choroid plexus of the fourth ventricle than the lateral ventricle
· Masses present in lateral ventricle are more clinically important, as they may grow to bemassive and compress adjacent tissue; they may also obstruct foramina of Monro and CSF outflow, leading to acquired hydrocephalus and increased intracranial pressure
· Mineralization possible
TYPICAL LIGHT MICROSCOPIC FINDINGS:
· Well circumscribed, often lobulated mass containing abundant cholesterol clefts, many foamy and hemosiderin-laden macrophages and multinucleated giant cells (foreign body reaction)
For gross findings:
· Choroid plexus papilloma or carcinoma: These are rare highly vascular papillary growths of meninges; neoplastic cells maintain choroidal appearance; resultant hydrocephalus is common
· Meningioma: Common in dog/cat, rare in cattle:
o Meningotheliomatous meningioma – neoplastic cells in sheets or pseudoalveoli on a vascular, collagenous stroma
o Psammomatous meningioma– neoplastic cells in whorls with central lamellar hyaline tissue and calcium/iron salts
o Angioblastic meningioma– neoplastic spindle cells surrounding endothelial cells in vessels lining vascular clefts
· Dog, cat, gerbil (over 50% affected by 2 years of age), rabbit, guinea pig: Aural cholesteatoma (masses of keratinized epithelium in external auditory canal); associated with chronic otitis externa or otitis media
Cholesterol granuloma reported in CNS of Russian viper snake, Cuban anole lizard, Cuban tree frog, leaf-tailed gecko, meerkat
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