Epidermoid cyst (CP angle)

Case contributed by A.Prof Frank Gaillard


1 week intermittent arm and leg weakness.

Patient Data

Age: 20
Gender: Female

Noncontrast scans were obtained through the brain for the purposes of stereotaxis. CSF density lesion seen in the right cerebellopontine angle displacing the brainstem to the left.


An extraaxial mass since the right of midline is seen anterior to the brainstem. Overall dimensions 45 millimeters transverse, 16 mm AP and 33 mm SI. The mass demonstrates bright T2 signal, low to intermediate T1 signal and internal restricted diffusion. No evidence of enhancement post administration contrast. Moderate mass effect on the brainstem. Moderate mass effect on the right fifth, seventh, eighth and lower cranial nerves. The basilar artery appears partially encased. The third and fourth cranial nerves are displaced cephalad. 


Findings consistent with a posterior fossa epidermoid.

Case Discussion

This is an absolutely classical example of an epidermoid cyst, and no differential should realistically be entertained. The patient went on to have a resection. 


MICROSCOPIC DESCRIPTION: The sections show strips of cyst lining which comprise a layer of keratinizing stratified squamous epithelium. A large amount of keratinous debris is present. The squamous cells show no evidence of dysplasia or malignancy. No adnexal structures are present. The features are those of an epidermoid cyst.

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Case information

rID: 28770
Published: 11th Apr 2014
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

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