|Year : 2013 | Volume
| Issue : 3 | Page : 215-217
Giant intradiploic infratentorial epidermoid cyst
Phani Kumar Mokkapaty1, Manisha Mohapatra2
1 Department of Neurosurgery, GSL Medical College, Rajahmundry, Andhra Pradesh, India
2 Department of Pathology, GSL Medical College, Rajahmundry, Andhra Pradesh, India
|Date of Web Publication||29-Aug-2013|
Phani Kumar Mokkapaty
80-26-10, Heritage Residency, A-3, A. V. Apparao Road, Rajahmundry - 533 103, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Epidermoid cysts are benign, uncommon lesions accounting for less than 1% of all intracranial tumors. Their location is intradiploic in 25% of cases, and rarely subtentorial. We report here a rare case of giant subtentorial intradiploic epidermoid cyst in a thirty year old patient who presented with subcutaneous retromastoid swelling. Computerized Tomography (CT) scan and Magnetic Resonance (MR) imaging revealed a giant osteolytic extradural lesion of the posterior fossa. Retrosigmoid suboccpital craniectomy and total removal of the tumor was done. Histopathological examination confirmed an epidermoid cyst. The outcome was good.
Keywords: Epidermoid cyst, intradiploic tumor, intracranial tumors
|How to cite this article:|
Mokkapaty PK, Mohapatra M. Giant intradiploic infratentorial epidermoid cyst. J NTR Univ Health Sci 2013;2:215-7
| Introduction|| |
Intradiploic epidermoid cysts are fairly uncommon lesions in neurosurgical practice. They are generally slow-growing benign congenital neoplasms, arising from the ectodermal cells within the neural groove between the 3 rd and 5 th weeks of embryogenesis at the time of its closure to form the neural tube, and subsequently remain within the cranial bones.  Epidermoid tumors generally account for 0.4-1.8% of all intracranial lesions, usually arising in cerebellopontine angle (CPA), parasellar area, and rhomboid fossa, and often growing extensively before presenting with clinical symptoms. Symptoms comprise either a palpable lump or focal neurological dysfunction from compression of adjacent neural structures.  Correct diagnostic radiological assessment with CT and MRI followed by total surgical removal is the ideal treatment. We report a case of a giant intradiploic epidermoid cyst and review the pertinent literature.
| Case Report|| |
A 30-year-old lady presented with history of a slowly growing painless swelling behind the left ear since six years [Figure 1]. Onset of headache and imbalance while walking prompted her to consult us. On examination she was found to have a 6 cm × 8 cm soft non-tender immobile globular mass in the left retromastoid region. The skin over the swelling could not be retracted and appeared normal. Neurological examination revealed the presence of left cerebellar signs including gait ataxia.
The CT scan showed an extradural expansive giant hypodense osteolytic lesion of the occipital bone in the left posterior fossa compressing the cerebellum and fourth ventricle. The lesion measured 6 cm × 8 cm with pericapsular calcifications, occipital bone erosion with total destruction of inner as well as outer tables. The lesion did not show any appreciable enhancement with contrast [Figure 2]. The MR imaging revealed a lesion of similar dimensions, hyperintense on T2, and hypointense on T1-weighted images [Figure 3].
|Figure 2: Non-contrast computerized tomography of the brain showing 6 cm × 8 cm size extradural expansive hypodenseosteolyticlesion of the occipital bone in the left posterior fossa|
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|Figure 3: MR imaging showing a lesion of 6 cm × 8 cm size extradural in location and hyperintense on T2|
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Left retrosigmoid suboccipital craniectomy and total excision of the tumor was performed. Macroscopically, the tumor was pearly white, friable, avascular, waxy, and smooth. The capsule was found to be thin and could be dissected off the dura. Within the tumor were multiple pieces of hair along with eroded bony fragments. At the end of the resection, the operated area was thoroughly irrigated with plain saline to wash out any residual capsule and tumor fragments. The microscopic examination revealed the tumor to be cystic, lined by stratified squamous keratinised epithelium along with presence of numerous layers of keratin. There were no areas of calcification or hemorrhage. The histopathological examination confirmed the diagnosis of intradiploic epidermoid cyst [Figure 4]. The post-operative course of the patient in the ward was uneventful and patient was discharged on 7 th post-operative day. The patient is doing well at the end of one year follow-up [Figure 5].
|Figure 4: Photmicrograph showing tumor with cyst and lined by stratified squamous keratinized epithelium along with presence of numerous layers of keratin (Hematoxylin and eosin, ×400)|
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| Discussion|| |
Epidermoid tumors are slow growing benign tumors. They grow by the accumulation of keratin and cholesterol, which are breakdown products created by the desquamation of epithelial cells.
Epidermoid tumors account for 0.4-1.8% of the cranial tumors, 75% of which are located intradurally and 25% are located within the diploic spaces. They are most commonly present in the 3 rd or 4 th decade of life as a long-standing painless subcutaneous scalp swelling covered with normal skin.  We found only five documented cases in the literature of giant intradiploic infratentorial epidermoid cysts. ,
Most epidermoid cysts are thought to result from a displacement of ectodermal tissue during the 3 rd to 5 th week of embryogenesis.  The most common presentation of the cranial intradiploic epidermoid is a long standing asymptomatic swelling of the scalp. Headache and focal tenderness may be present with progression of the lesion. Giant lesions may be associated with focal neurological signs. Super-infection due to erosion of skin or bleeding has been described.  Malignant transformation though rare may occur with large lesions of very long standing duration. 
A well-defined lytic lesion centered in the diploic space with or without sclerotic margins is visualized on a CT scan.  Both inner and outer tables are involved with complete destruction of bone on progression of the lesion as was seen in our case. MR imaging reveals that these cysts are consistently hyperintense on T2-weighted images.  No contrast enhancement is present unless the lesion is super-infected.
Surgical excision of the cyst is performed for diagnosis, to relieve any symptoms, for cosmetic improvement and to avoid potential complications, which include intracranial mass effect, abscess formation, bleeding, and malignant change. Surgery is performed with the goal being total removal of the capsule. The capsule is the only living and growing part of the neoplasm and hence must be carefully dissected from the bone and dura mater. A patient and meticulous microscopic dissection of firm portions of capsule lessen the risk of morbidity and mortality. Partial resection of intradiploic epidermoids can lead to tumor recurrence. Hence, an aggressive total removal, whenever it is possible, is recommended, avoiding spilling of tumor material and using copious irrigation of surgical field with 0.9% saline to prevent aseptic meningitis.
| Conclusion|| |
Intradiploic epidermoid tumors are benign, slow growing lesions that should be completely excised. Correct radiological assessment of these lesions with MRI and CT scan and complete removal of the tumor with its capsule are essential for adequate surgical treatment, thereby, providing a good long-term prognosis for the patient.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]