CASE 13385 Published on 06.02.2016
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Intradiploic epidermoid cyst with osteolytic lesions of the skull.

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Anastasia Zikou1, Aristeidis Katsanos2, Anna Gousia3, Andreas Zygouris4, Vasileios Xydis1, Maria I Argyropoulou1.

1. Department of Clinical Radiology, Medical School of Ioannina, Greece.
2. Department of Neurology, Medical School of Ioannina, Greece.
3. Department of Pathology, Medical School of Ioannina, Greece.
4. Department of Neurosurgery, Medical School of Ioannina, Greece.

Email: anzikou@cc.uoi.gr
Connected authors
Patient

45 years, female

Categories
Area of Interest Neuroradiology brain ; Imaging Technique CT, MR, MR-Diffusion/Perfusion, Experimental
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Clinical History
A 45-year-old woman with a history of headaches. Clinical examination revealed a small painless bony swelling under the scalp over the right occipital region. Brain CT and ΜRI were performed.
Imaging Findings
CT revealed an osteolytic lesion of the right occipital bone (Fig.1). On MRI axial T2-weighted and FLAIR images demonstrated an inhomogeneous hyperintense lesion in the right occipital intradiploic space (Fig.2-3). Axial post gadolinium T1-weighted images showed minimal peripheral contrast enhancement (Fig.4). Restricted diffusion observed on ADC maps was suggestive for the diagnosis of epidermoid cyst (Fig.5). Histology after lesion biopsy confirmed the diagnosis (Fig.6).
Discussion
Intradiploic epidermoid cysts are derived from the ectodermal cells of the cranium and are lined solely by stratified squamous epithelium. Microscopically the wall of the cystic tumour is lined by squamous epithelium and the cyst is filled with lamellated keratin content. Epidermoid cysts are extremely rare; common locations include the occipital, frontal, and parietal bones. Since these cysts grow very slowly, the onset of symptoms and signs is often late, over a period of months to years. These lesions usually present as painless bony swelling under the scalp. They may cause headaches due to erosion of the calvarium, and seizures due to local pressure. These lesions may perforate the dura, rupture into the subarachnoid space with resulting chemical meningitis, or involve the brain parenchyma. They are hypoattenuating lesions on CT scans. MRI shows inhomogeneous hypointense signal on T1 weighted images and inhomogeneous hyperintense on T2 and FLAIR images. Lesions typically do not enhance. When present, contrast enhancement is minimal and peripheral. DWI is the best imaging sequence in diagnosing epidermoid cysts since they show restricted diffusion due to keratin content (1-3).
Differential Diagnosis List
Intradiploic epidermoid cyst.
dermoid cyst
sebaceous cyst
Final Diagnosis
Intradiploic epidermoid cyst.
Case information
URL: https://www.eurorad.org/case/13385
DOI: 10.1594/EURORAD/CASE.13385
ISSN: 1563-4086
License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Figure 1

CT

CT
Computed tomography scan with bone density window reveal an occipital osteolytic lesion (arrows).
Figure 2

MRI-1

MRI-1
Axial T2-weighted images demonstrate an inhomogeneous hyperintense lesion in the right occipital intradiploic space (arrows).
Figure 3

MRI-2

MRI-2
Axial FLAIR images demonstrate an inhomogeneous hyperintense lesion in the right occipital intradiploic space (arrows).
Figure 4

MRI-3

MRI-3
Axial post gadolinium T1-weighted MR images show minimal and peripheral contrast enhancement (arrows).
Figure 5

MRI-4

MRI-4
The ADC maps reveal restricted diffusion (arrows).
Figure 6

Photomicrograph

Photomicrograph
Photomicrograph from tissue sections of the lesion shows the cyst with keratinized squamous epithelial lining, filled with keratin (H-E ×100). The histological diagnosis was consistent with an epidermoid cyst.