Annika Mascarenhas, Alyssa Parsons, Caroline Smith, Cindy Molloy, Alistair Jukes
  1. Department of Neurosurgery, Women's and Children's Hospital, North Adelaide, Australia
  2. Department of Anatomical Pathology, SA Pathology, Adelaide, Australia
  3. Department of Neurosurgery, Royal Adelaide Hospital, Adelaide, Australia

Correspondence Address:
Annika Mascarenhas
Department of Neurosurgery, Royal Adelaide Hospital, Adelaide, Australia


Copyright: © 2017 Surgical Neurology International This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

How to cite this article: Annika Mascarenhas, Alyssa Parsons, Caroline Smith, Cindy Molloy, Alistair Jukes. Malignant squamous cell carcinoma arising in a previously resected cerebellopontine angle epidermoid. 10-Aug-2017;8:186

How to cite this URL: Annika Mascarenhas, Alyssa Parsons, Caroline Smith, Cindy Molloy, Alistair Jukes. Malignant squamous cell carcinoma arising in a previously resected cerebellopontine angle epidermoid. 10-Aug-2017;8:186. Available from:

Date of Submission

Date of Acceptance

Date of Web Publication


Background:Malignant squamous cell differentiation of an epidermoid cyst can carry a significantly poor prognosis and very little is known about this entity.

Case Description:We present the case of a 35-year-old lady, with primary malignant squamous cell carcinoma (SCC) arising from a previously partially resected cerebellopontine angle epidermoid cyst almost 5 years after initial resection. We also review the relevant literature.

Conclusion:The imaging findings, histopathology, and management of a malignant SCC arising from a benign epidermoid cyst are discussed with recommendation for increased surveillance and follow-up, even for classically accepted benign lesions.

Keywords: Cerebellopontine angle tumour, Epidermoid, Squamous cell carcinoma, Malignant transformation


Epidermoid cysts are benign, slow growing, extra-axial tumors that account for ~1% of all intracranial tumors. Embryologically, they are derived from ectodermal inclusions during neural tube closure.[ 6 ] Intracranial squamous cell carcinoma (SCC) is commonly seen as a metastatic deposit, however, there are case reports of malignant transformation of epidermoid into SCC. We present the case of a 35-year-old female with primary malignant SCC arising in a partially resected cerebellopontine angle (CP angle) epidermoid.


The patient originally presented in 2010 with headaches. Neurological exam was unremarkable. Magnetic resonance imaging (MRI) demonstrated a CP angle lesion that was lobulated and predominantly of low signal intensity in the prepontine and right ambient cistern, with a few small foci of increased signal intensity on diffusion imaging, which was consistent with an epidermoid along with a small left-sided acoustic neuroma. At that time, a right retrosigmoid craniotomy was performed with the intention of decompressing the brainstem and cranial nerves. The right CP angle lesion was partially resected with a small residual left coating the anterior brainstem in the prepontine cistern. Histology demonstrated an epidermoid tumor with typical histological features of lamellar keratin and benign squamous epithelium. The small residual was monitored with serial MRI scans. Approximately 5 years later, routine follow-up MRI demonstrated marked growth of the residual lesion with development of a multilobulated enhancing cystic component. The patient complained of a 6-month history of right-sided facial numbness. After discussion with the patient, the decision was made to reoperate and resect this lesion. A repeat right retrosigmoid craniotomy was performed. Intraoperatively, the lesion was cystic with an anteromedial solid component adhering to the lateral aspect of the brainstem. There appeared to be a dural attachment which was resected. The patient awoke well initially, however, subsequently developed a House–Brackmann grade 5 facial palsy on day 2 [ Figure 1 ].

Figure 1

(a) MRI T2 CIS axial demonstrating pre-pontine and ambient cistern lesion in 2010. (b) MRI T1 post gadolinium in 2010 demonstrating no significant enhancement. (c) MRI T1 post gadolinium in 2015 demonstrating no significant enhancement. (d) MRI T1 post gadolinium in 2016 demonstrating lobulated, enhancing mixed cystic/solid lesion


Pathological findings

Histology demonstrated SCC with areas of poorly differentiated sarcomatoid elements. The squamous component comprised large epithelial cells with hyperchromatic, pleomorphic nuclei, and abundant, dense eosinophilic cytoplasm. Keratinization and intercellular bridges were present. There were no benign squamous cellular features. An acellular keratin pearl was present. The sarcomatoid component comprised highly atypical spindle cells displaying hyperchromatic, pleomorphic nuclei, and brisk mitotic activity. Areas of necrosis were also present. Immunohistochemistry was performed. The squamous cell component was positive for CK5/6, and had positive nuclear staining for P63. Some of the sarcomatoid spindle cells showed positive staining for cytokeratin markers AE1/3 and CK5/6 and P63. They were negative for CD34, S100, desmin, GFAP, CD31, and myogenin. The previous histology was reviewed which showed benign squamous cyst wall and keratin. There were no malignant features [ Figure 2 ].

Figure 2

(a) first histology H and E staining demonstrating benign squamous cyst wall and keratin with no malignant features. (b) Second resection histology H and E staining showing metastatic squamous cell carcinoma features. (c) and (d) immunohistochemistry staining demonstrating malignant squamous cell markers of CK 5/6 and positive nuclear staining for P63



Malignant transformation of an epidermoid tumor into SCC is a rare but described phenomenon.[ 1 4 5 8 9 10 11 ] By far the most common cause of intracranial SCC is metastasis from elsewhere. True primary SCC is thought to arise from malignant transformation of a dermoid or epidermoid within the central nervous system.[ 3 7 ] Garcia first described this in 1981 and proposed a set of criteria for the diagnosis of primary squamous cell carcinoma; Tumor restricted to the intracranial compartment, no invasion or extension beyond the dura or cranial bones, no communication with the middle ear, air sinuses or sella, no evidence of nasopharyngeal tumor.[ 3 ] Hamlat et al. added to this in 2005, proposing that there also be benign squamous epithelium within the main tumor mass and no evidence of a primary tumor elsewhere.[ 4 ] Prognosis has been considered poor across the literature with a median survival of 9 months, although this has been increased to 26 months in some cases with radiotherapy.[ 2 ] Any rapid growth of a lesion in the site of a previously resected epidermoid or dermoid or change in the MRI characteristics of any residual should be considered suspicious and prompt either operative intervention to gain tissue for analysis or a more frequent surveillance schedule.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


1. Acciarri N, Padovani R, Foschini MP, Giulioni M, Finizio FS. Intracranial squamous cell carcinoma arising in an epidermoid cyst. Br J Neurosurg. 2009. 7: 565-9

2. Agarwal S, Rishi A, Suri V, Sharma MC, Satyarthi GD, Garg A. Primary intracranial squamous cell carcinoma arising in an epidermoid cyst-a case report and review of literature. Clin Neurol Neurosurg. 2007. 109: 888-91

3. Garcia CA, McGarry PA, Rodriguez F. Primary intracranial squamous cell carcinoma of the right cerebello-pontine angle. J Neurosurg. 1981. 54: 824-8

4. Hamlat A, Hua ZF, Saikali S, Laurent JF, Gedouin D, Ben-Hassel M. Malignant transformation of intra-cranial epithelial cysts: Systematic article review. J Neurooncol. 2005. 74: 187-94

5. Lakhdar F, Hakkou el M, Gana R, Maaqili RM, Bellakhdar F. Malignant transformation six months after removal of intracranial epidermoid cyst: A case report. Case Rep Neurol Med 2011. 2011. p.

6. Law EK, Lee RK, Ng AW, Siu DY, Ng HK. Atypical intracranial epidermoid cysts: Rare anomalies with unique radiological features. Case Rep Radiol 2015. 2015. p.

7. Nagasawa DT, Choy W, Spasic M, Yew A, Trang A, Garcia HM. An analysis of intracranial epidermoid tumors with malignant transformation: Treatment and outcomes. Clin Neurol Neurosurg. 2013. 115: 1071-8

8. Raheja A, Eli IM, Bowers CA, Palmer CA, Couldwell WT. Primary Intracranial Epidermoid Carcinoma with Diffuse Leptomeningeal Carcinomatosis: Report of Two Cases. World Neurosurg. 2016. 88: 692.e9-16

9. Shah A, Goel A, Goel N. A case of cerebellopontine angle epidermoid tumor and brainstem squamous cell carcinoma presenting as collision tumor. Acta Neurochir (Wien). 2010. 152: 1087-8

10. Tognetti F, Lanzino G, Manetto V, Calbucci F. Intracranial squamous cell carcinoma arising in remnant of extirpated epidermoid cyst. Br J Neurosurg. 2009. 5: 303-5

11. Vellutini EA, de Oliveira MF, Ribeiro AP, Rotta JM. Malignant transformation of intracranial epidermoid cyst. Br J Neurosurg. 2014. 28: 507-9

Leave a Reply

Your email address will not be published. Required fields are marked *