ependymomas are thought to arise from ependymal cells lining the cerebral ventricles and the central canal of the spinal cord . although they can arise throughout the neuroaxis , they are most commonly found in the posterior fossa in children , and the spinal cord in adults . supratentorial ependymomas are rare and can appear very similar to other primary central nervous system ( cns ) tumours such as oligodendroglioma , central neurocytoma or pilocytic astrocytoma . . we present a rare case of supratentorial ependymoma that presented as an isolated cortical cyst with a mural nodule in a 27-year - old woman and discuss the differential diagnosis of cyst with a mural nodule in the brain . magnetic resonance imaging ( mri ) revealed a 2.8  2.9 cm lesion in the left parietal lobe , which was predominantly cystic with a murally enhancing nodule ( fig .  1 ) . the cyst content was isointense to cerebrospinal fluid ( csf ) on t1- and t2-weighted imaging . figure  1:mri of a supratentorial ependymoma that presents as a single cyst with a contrast - enhancing mural nodule . mri of a supratentorial ependymoma that presents as a single cyst with a contrast - enhancing mural nodule . ( a ) t1-weighted axial image with contrast . ( b ) t2-weighted axial image . ( d ) t1-weighted image in a sagittal plane with contrast . the possibility of pilocytic astrocytoma was entertained and the patient was offered surgery after discussion in a specialist multidisciplinary team meeting . a left parietal craniotomy and gross total resection of the lesion was performed under image guidance . the tumour had a large cystic component containing straw - coloured , xanthochromic fluid and a solid 1.0  1.5  2.0 cm nodule . it was well demarcated from the surrounding parenchymal tissue , and there was no communication with the ventricular system . a gross total microscopic resection of the tumour was performed and there were no intraoperative or postoperative complications . the histopathological examination revealed a moderately cellular tumour comprising variably pleomorphic cells with fibrillary processes and mainly rounded nuclei with a coarsely speckled chromatin pattern . the fibrillary processes of the tumour cells frequently were arranged around the tumoural blood vessels in a radial manner forming perivascular pseudorosettes . no areas showing high cell density , microvascular endothelial proliferation or necrosis were evident and mitotic activity was inconspicuous . immunostaining for glial fibrillary acid protein ( gfap ) showed widespread labelling in the cytoplasm and processes of the tumour cells . immunostaining for epithelial membrane antigen ( ema ) revealed frequent perinuclear dot - like labelling as well as highlighted occasional ependymal canals characteristic of ependymal tumours . r132h mutation in the idh1 gene is the most common mutation seen in diffusely infiltrative gliomas such as diffuse astrocytomas and oligodendrogliomas , but not observed in ependymal tumours . overall , the histological features were consistent with a conventional ependymoma ( who grade ii ; fig .  2 ) . the patient was discharged on day 5 postop and followed up with serial mri . haematoxylin and eosin - stained section ( a ) shows a moderately cellular tumour with frequent perivascular pseudorosettes and areas of stromal microcalcifications ( inlet in a ) . immunostaining for gfap reveals widespread labelling in the tumour cells ( b ) ; whereas that for ema shows frequent perinuclear dot - like labelling and accentuates occasional small ependymal canals ( c ) . scale bar : 100 m ( a and b ) , 20 m ( c and d ) , 60 m ( inlet in a ) . haematoxylin and eosin - stained section ( a ) shows a moderately cellular tumour with frequent perivascular pseudorosettes and areas of stromal microcalcifications ( inlet in a ) . immunostaining for gfap reveals widespread labelling in the tumour cells ( b ) ; whereas that for ema shows frequent perinuclear dot - like labelling and accentuates occasional small ependymal canals ( c ) . scale bar : 100 m ( a and b ) , 20 m ( c and d ) , 60 m ( inlet in a ) . the classic radiological features of a cyst with the mural nodule are usually observed with low - grade pathologies such as ipilocytic astrocytoma ( peak age 515 years ) and haemangioblastoma ( peak age 4060 years ) . these tumours are most commonly found in the posterior fossa , and the cyst content is usually slightly hyperintense to csf on t1-weighted imaging . other tumours with cyst with a mural nodule appearance are pleomorphic xanthoastrocytoma ( peak age 1030 years ) , ganglioglioma ( peak age 1020 years ) and desmoplastic infantile ganglioglioma ( peak age 12 years ) . these tumours are usually found in the supratentorial compartment and the cystic portion is hypointense on t1-weighted mri . very rarely , metastatic tumours can also present as cyst with a mural nodule . to our knowledge , this is the first reported case of supratentorial ependymoma presenting as a pure cortical cyst with the mural nodule in an adult . only one previous report of such lesion was found in a 9-year - old boy . a review of the literature reveals that supratentorial ependymomas tend to be different from their infratentorial counterparts : first , while the majority of infratentorial tumours are intraventricular , supratentorial ependymomas are usually intraparenchymal . for example , supratentorial ependymomas may arise from foetal rests of ependymal cells that are located in the angle of the ventricles deep within the cerebral parenchyma . secondly , a higher proportion of supratentorial ependymomas are high grade ( 5060% ) compared with infratentorial ependymomas ( 1040% ) . thirdly , in gene expression profiling studies , supratentorial tumours cluster separately to posterior fossa and spinal cord tumours , suggesting that they represent a molecularly disparate group of tumours . in conclusion , supratentorial ependymoma is a rare tumour , which can rarely present as a single cortical cyst with a mural nodule on imaging . the possibility of ependymoma should be considered in any case of supratentorial cyst with the mural nodule .
supratentorial ependymoma is a rare tumour in the adult central nervous system . 
 we present an unusual case of supratentorial ependymoma in a young adult that presented as a pure cortical cyst with a mural nodule and discuss the differential diagnosis of such lesions in the brain .