primary spinal cord tumors account for 4 - 8% of central nervous system tumors . in adults , ependymoma is the most common primary spinal cord tumor followed by astrocytomas , which are rare tumors constituting 6 - 8% of spinal cord tumors . cervical and thoracic regions of the spine are the most common locations for spinal astrocytomas to occur , with only 4% of all spinal astrocytomas occurring in the conus - cauda equina region . it is thus rare for astrocytomas to occur in the conus - cauda region , where myxopapillary ependymomas account for 80% of the tumors . astrocytomas are typically intramedullary tumors and occurrence of a predominantly extramedullary astrocytoma is extremely rare . we describe such a rare case of giant extramedullary pilocytic astrocytoma of cauda equina . to the best of our knowledge , giant extramedullary pilocytic astrocytoma of cauda equina has not been previously described in the available english literature . a 20-year - old male patient presented to us with complaints of progressive weakness in bilateral lower limbs , saddle anesthesia and bladder dysfunction for past 2 years . clinical examination revealed weakness of bilateral lower limbs ( medical research council grade : 4/5 ) , asymmetrical sensory loss in bilateral l5-s3 distribution . magnetic resonance imaging ( mri ) of the lumbosacral spine showed an intradural lesion that extended from l4 to s4 vertebral segments causing scalloping of the posterior surface of vertebral bodies and expansion of the spinal canal . the conus medullaris was low lying and reached up to the level of l4 vertebral body . a screening mri of the rest of the cranial - spinal axis was done to rule out any other lesion was done . however , patient was found to have right cerebellopontine angle enhancing lesion suggestive of acoustic schwannoma and another lesion in the suprasellar region suggestive of hypothalamic glioma [ figure 2 ] . t1-weighted sagittal ( a ) and axial ( d ) images show a hypointense intradural lesion within the spinal canal extending from l4 to s4 spinal segments , causing scalloping of the posterior surface of vertebral bodies and expansion of the canal . in t2-weighted sagittal ( b ) and axial ( e ) following contrast administration , mass lesion shows peripheral enhancement ( c and f ) brain magnetic resonance imaging showing associated right acoustic schwannoma ( a ) and suprasellar contrast enhancing lesion suggestive of hypothalamic glioma ( b - d ) . screening mri whole spine did not reveal any other spinal lesion ( e ) patient was operated in the prone position . a large intradural cystic lesion , with a thin cyst wall formed by the tumor tissue , was present in the lumbosacral region . yellowish , soft , mildly vascular tumor was covering the nerve roots of cauda equina and the filum terminale . the wall of the tumor and the filum terminale covered with the tumor were removed . the tumor draping the nerve roots was left behind as it entailed the risk of causing neurological deficits . as the patient was asymptomatic for intracranial lesions a decision to conservatively follow the patient was taken . photomicrographs showing a sparsely cellular tumor with interspersed rosenthal fibers and granular bodies and clearing of cytoplasm of some neoplastic cells ( a and b ; h and e , 200 and 400 respectively ) . tumor cells are immunoreactive for glial fibrillary acidic protein and mib 1 labeling index is low ( c and d 200 each ) during follow - up , patient 's bladder dysfunction improved gradually and presently patient is able to void himself . however , patient 's motor and sensory symptoms showed neither improvement nor deterioration during 2 years follow - up . follow - up mri revealed recurrence of the lesion [ figure 4 ] . t1-weighted ( a ) , t2-weighted ( b ) and contrast ( c ) sagittal views and axial t2-weighted ( d ) and contrast images ( e ) show recurrent tumor pilocytic astrocytomas of conus - cauda region are very rare . in a study of 79 patients with intramedullary astrocytomas by minehan et al . rarely astrocytomas may have an exophytic component ; however , extramedullary gliomas of cauda equina region are extremely rare with only few cases reported in the literature and a giant pilocytic astrocytoma of cauda equina has not been previously described in the available english literature . bailey was the first to suggest the glial heterotopias as the site of origin of extramedullary gliomas . patient was operated with a clinical impression of meningioma , but histopathology revealed its true identity to be an astrocytoma . in our case also , there was a preoperative diagnostic dilemma with regard to nature of the lesion and a possibility of giant cystic schwannoma was considered , though lack of involvement of foramina was against this diagnosis . this case emphasizes the need to consider pilocytic astrocytoma in the differential diagnosis of cystic cauda equina tumors . to the best of our knowledge , this is the first case of a giant cauda equina pilocytic astrocytoma in the literature ; though , there have been few reports of extramedullary astrocytoma of conus region . singh et al . reported an extramedullary astrocytoma of conus region with no attachment to surrounding neural structures . it adds another differential in the list of differential diagnoses of cystic cauda equina lesions . the management of pilocytic astrocytomas of spinal cord involves surgery with or without adjuvant radiation therapy . as these lesions are benign , the patients can be followed - up after surgery and radiation therapy can be given in case of recurrence / regrowth .
astrocytomas of conus - cauda equina region are rare . astrocytomas , which are intramedullary tumors , may rarely have an extramedullary component . however , primary intradural extramedullary astrocytomas are extremely rare , with very few cases reported in the literature . 
 we describe a giant extramedullary pilocytic astrocytoma of cauda equina in a 20-year - old male . to the best of our knowledge , 
 this is the first report of such a case in the available literature . 
 this case highlights the fact that astrocytomas can be primarily extramedullary and emphasizes the need to consider pilocytic astrocytoma in the differential diagnosis of cystic cauda equina tumors .