Epidermoid cyst with dystrophic calcification

Case contributed by Assoc Prof Frank Gaillard



Patient Data

Age: 60 years

There is a very large heterogeneous density intracranial mass lesion is mostly of fluid attenuation with areas of calcification and fat density demonstrates a rim of smooth post-contrast enhancement. The lesion results in 15 mm of left-to-right midline shift and marked mass effect with distortion of the left lateral ventricle and effacement of the third ventricle leading to obstructive hydrocephalus of the right lateral ventricle as well as left uncal herniation, but no tonsillar herniation. There is also periventricular interstitial edema, consistent with acute hydrocephalus. There are pockets of fat density surrounding the mass, particularly anteriorly, and the lesion probably arises from the skull vault in the region of the junction of the left frontal and temporal bones with growth inwards. No acute displaced skull fracture. There is mild mucosal thickening in the ethmoid air cells. The other visualized paranasal sinuses, mastoid air cells and middle ear clefts are well-aerated.

Conclusion: Large fat-containing intracranial mass lesion with surrounding fat density, probably arising from the skull vault likely represents a large dermoid/epidermoid. 

There is a large extra-axial heterogeneous mass that grossly indents the left frontal lobe. The lesion demonstrates heterogeneous T1 and T2 signal with a thin rim of contrast enhancement along its anterior and medial margins, and calcification within its anterior and posterior rim. The bulk of the central lesion suppresses on FLAIR, but demonstrates intermediate diffusion restriction (~900 x 10-6 cm2/s). The peripheral component of the mass demonstrates intermediate T1/T2 signal.

Anterior to the mass are fat signal lobules that may represent ruptured elements. Spectroscopy (not shown) demonstrates elevated lactate peak within parts of the lesion. No elevated CBV/CBF within the lesion. Mass compresses the left lateral ventricle, causing 15 mm of midline shift to the right and uncal herniation with effacement of the third ventricle and obstructive hydrocephalus. Remainder of the brain is unremarkable.


The majority of the mass has imaging appearances of an epidermoid cyst with dystrophic calcification, however the presence of fatty components suggests that this actually represents a dermoid cyst (with sebum) or (less likely) a mature cystic teratoma.

Intra-operative photos


Tract extending from retracted craniotomy flap to bone, followed by extra-axial mass seen after elevation of craniotomy flap. 

Photos courtesy of Dr Tanya Yuen, Neurosurgeon. 

Case Discussion

Patient went on to have resection of the mass. 



Sections show predominantly keratinous debris together with a fibrous cyst wall containing foci of dystrophic calcification and patchy chronic inflammation. No intact cyst wall lining is evident. Hemosiderin laden macrophages and cholesterol clefts are present, consistent with previous hemorrhage. No skin adnexal structures are seen. There is no evidence of malignancy. 

DIAGNOSIS: Epidermoid cyst.



This case remains a little unresolved. Clearly the majority of the mass is an epidermoid cyst, which is the favored imaging feature. The clearly fatty components are unusual, and most likely this represents a variation of a white epidermoid cyst; a rare variant where abundant lipids result in lower CT values and T1 shortening. I am unable to find a reference for whether or not white epidermoids suppress on fat saturated sequences. 



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