Figure 1
Plain radiograph of the skull, lateral view
Plain radiograph of the skull, lateral view shows a large, well-defined radiolucent lesion with sclerotic, scalloped edges in the parietal bone.
Clinical History
The patient consulted after a car accident complaining of persistent headache. Physical examination of the skull revealed a palpable lump in the left parietal area. The patient mentioned frequent headaches and motoric disturbances during the last three months.
Imaging Findings
The patient consulted after a car accident complaining of persistent headache. Physical examination of the skull revealed a palpable lump in the left parietal area. The patient mentioned frequent headaches and motoric disturbances during the last three months.
A conventional radiograph, a CT scan and a MRI of the brain and skull were performed.
Discussion
Epidermoids make up less than one percent of all intracranial masses. Within the group of congenital intracranial masses, epidermoid is the most frequent lesion, followed by lipoma, dermoid and teratoma. Embryologically the tumor arises from incorporation of one or more of the three germ layers. If inclusion is early, the lesion is midline in localization, if extremely late, it becomes intradiploic.
The age of presentation ranges from 25 to 60. The male to female ratio is 2 to 1. The relative absence of neurologic deficits is probably due to the slow growth rate. Epidermoids differ from dermoid cysts in having a distinct granular layer, containing laminated keratin without skin adnexa. Intra-osseous epidermoids are rare. They arise in the distal phalanx, mandibula, maxillary bone, tibia and femur but mainly in the neurocalvarium. Epidermoids may have a multilobulated grayish-white macroscopic appearance and are often referred to as "pearly-tumors". An extradural mass is more easily recognized on plain film, because of its well-defined radiolucency and erosion of the adjacent tabula. The edges are sclerotic. On CT scan epidermoids show a low density which reflects their composition in two major components: keratin within cellular debris and cholesterol crystals. Calcification is an uncommon finding. The absence of enhancement on contrast enhanced CT scan is a constant finding, because of the avascular nature of these tumors. Epidermoids are usually hyperintense on SE T2-weighted images. However the appearance of epidermoid tumors is quite variable on SE T1-weighted images, depending on their contents.
Differential Diagnosis List
Epidermoid Cyst
Final Diagnosis
Epidermoid Cyst
References
[1] Guiard JM, Kien P, Colombani S et al. Kystes 退pidermodes diploques de l'adulte. Apport de la tomodensitom退trie propos de 6 nouveaux cas. J Neuroradiol 1986; 13 (1): 22-31. (PMID: 3746436)
[2] Dias PS, Pay PL. Giant epidermoid cysts of the skull. Br J Neurosurg 1989; 3 (1): 51-58. (PMID: 2789714)
[3] Smirniotopoulos JG, Le SH. Cranial MRI and CT. Mosby, St Louis 1994; 8: 345-347.
Case information
| URL: | https://eurorad.org/case/902 |
| DOI: | 10.1594/EURORAD/CASE.902 |
| ISSN: | 1563-4086 |
Figure 2
Non-enhanced CT scan of the brain and skull
Non-enhanced CT scan of the brain and skull, soft tissue window setting demonstrates in the left parietal area an intradiploic, expansile, inhomogeneous, hypodense lesion. The lesion is sharply demarcated with a small hyperdense rim. There is focal interruption of the inner table. Densities vary between 22 and 28 HU.
Figure 3
Magnetic Resonance Imaging Studies
MRI of the brain and skull shows, on SE T1-weighted images, the tumor displaying heterogeneous signal characteristics with central hypointense region and hyperintense peripheral rim.
On SE T2-weighted images the lesion is inhomogeneous and mostly hyperintense.
On SE T1-weighted images after intravenous administration of contrast medium there is no enhancement of the lesion.
Plain radiograph of the skull, lateral view
Plain radiograph of the skull, lateral view shows a large, well-defined radiolucent lesion with sclerotic, scalloped edges in the parietal bone.
Non-enhanced CT scan of the brain and skull
Non-enhanced CT scan of the brain and skull, soft tissue window setting demonstrates in the left parietal area an intradiploic, expansile, inhomogeneous, hypodense lesion. The lesion is sharply demarcated with a small hyperdense rim. There is focal interruption of the inner table. Densities vary between 22 and 28 HU.
Magnetic Resonance Imaging Studies
MRI of the brain and skull shows, on SE T1-weighted images, the tumor displaying heterogeneous signal characteristics with central hypointense region and hyperintense peripheral rim.
On SE T2-weighted images the lesion is inhomogeneous and mostly hyperintense.
On SE T1-weighted images after intravenous administration of contrast medium there is no enhancement of the lesion.