Intracranial epidermoid cyst

Histology Report:

MACROSCOPIC DESCRIPTION: "Brain tissue for histo": An aggregate of friable pale/light brown pearly tissue fragments in total 50x50x5mm with fragments up to 20mm. 

MICROSCOPIC DESCRIPTION: The sections show sheets of anuclear squamous epithelium and hyperkeratosis with some whorled architecture. There are no viable keratinocytes and there are occasional foci of fibroblasts, inflammatory cells and haemosiderin laden macrophages. There are no adnexal components. There is no brain parenchyma and there is no evidence of malignancy.

DIAGNOSIS: Brain tissue: Anuclear keratin debris consistent with epidermoid cyst.

Irregular lobulated right cerebellopontine angle extra-axial mass extending into the right middle cranial fossa, measuring approximately 64 x 63 x 65 mm. The lesion is predominantly T1 hypointense and T2 hyperintense with elevated signal on DWI, partial FLAIR suppression and no enhancement. No suspicious susceptibility. Slight extension into the right IAC. Severe mass effect upon the brainstem, with distortion, effacement and displacement; less severe mass effect on the right cerebellum, thalamus and temporal lobe. No abnormal parenchymal signal/oedema. 8 mm of midline shift to the left.

No abnormal enhancement elsewhere in the brain. The dural venous sinuses are patent with an normal T2 flow voids. Normal appearance of the clivus and dorsum sella. Small left retrocerebellar arachnoid cyst.

A 14x13x20mm well defined high T2 lesion with enhancement  alongalong the mastoid segment of the right facial nerve is most likely a neurogenic tumour.

Mucosal thickening and fluid within the maxillary sinuses.

Conclusion:

Findings most in keeping a large right cerebellopontine angle epidermoid cyst with marked distortion of the brainstem and supratentorial extension. Likely

A neurogenic tumour along the mastoid segment of the right facial nerve.