subependymoma , first described by scheinker in 1945 , is a rare central nervous system tumor . since its first description in the spinal cord by boykin et al in 1954 , 32 involved the cervical cord . in the spinal region , these lesions are predominantly subpial in location , with exophytic components . the location of these lesions in the spinal cord suggest a subpial glial progenitor origin rather than its proposed origin from subependymal progenitor cells.[14 ] a 37-year - old lady presented to us with complaints of neck pain and gait disturbances of 1 year duration with severe progressive weakness of her right upper limb since 3 months . mri revealed a long - segment t2 hyperintense intramedullary lesion opposite to the c3 to d4 vertebral levels with mild heterogeneous enhancement on the post contrast study [ figure 1 ] . ( a ) sagittal t2 and ( b ) post contrast t1-weighted mr images showing a long segment t2 hyperintense and mild hetrogenous enhancing lesions in the cervical cord , showing cord expansion . intraoperatively , the lesion was firm , with a poor plane of demarcation from the normal cord , and was seen intermingling with posterior and anterior nerve rootlets . it was eccentric in location , involving more of the left hemicord , with exophytic components [ figure 2 ] . surgical finding : typical exophytic subpial lesions , with lesion on either sides of the dorsal nerve roots . all of the resected tissue submitted for histopathological analysis was processed and embedded in three paraffin blocks . histopathological examination [ figure 3 ] revealed characteristic features of a subependymoma ( who grade 1 ) with small monomorphic cells arranged in a lobular pattern against a finely fibrillary background , with occasional rosette like pattern . features of pleomorphism , mitotic activity , endothelial cell proliferation , and necrosis were not seen . the mib-1 proliferative index was low ( < 1% of tumor cells ) ( ) . immunohistochemistry revealed diffuse positivity for glial fibrillary acidic protein ( gfap ) , whereas tumor cells failed to express epithelial membrane antigen ( ema ) . histopathology : ( a ) h and e staining shows lobular pattern arrangement of monomorphic nuclei in fibrillary pattern ( 400 ) . ( b ) mib-1 labeling index is less than 1% of tumor cells ( not shown in figure ) ( 400 ) . immunohistochemistry for ( c ) gfap highlights diffusely positive tumor cells in a fibrillary background ( 400 ) ( d ) tumor cells are negative for ema ( 400 ) she did not receive any adjuvant treatment and has been on follow up for 6 months with periodic mr imaging . subependymomas are rare central nervous system tumors accounting for 0.7% of all intracranial neoplasms and 8.3% of all ependymal tumors . they are located most frequently in the fourth ventricle ( 5060% of cases ) followed by the lateral ventricles ( 3040% ) . so far , only 47 cases have been reported in the english literature in the spinal cord ; of which 32 cases were located in the cervical , cervico - medullary , and cervico - thoracic locations . most are intramedullary in location , with few subarachnoid and extramedullary variants mentioned in the literature . the symptomatic subependymoma generally occur after 40 years of age and are rare in childhood.[13 ] the salient features 33 in cases of cervical subependymomas they have a mean age of presentation of about 44 years with a strong male preponderance [ table 2 ] . epidemiology of spinal subependymomas ( including our case).[16 , 814 ] histopathologically these tumors are low grade ( who grade 1 ) , characterized by homogenous cells with sparse cellularity showing clustering of nuclei over a fibrillary background formed by cell processes and occasional occurrence of microcysts . the tendency to form pseudorosettes and the cells being round with hyperchromatic nuclei are reminiscent of ependymomas . immunohistochemical characteristics are however identical to that of astrocytic neoplasms with diffuse gfap and s-100 protein positivity . in contrast to ependymomas , the former is evidenced by the processes containing intermediate filaments and the latter by microlumens , cilia , microvilli , and intercellular junctions . the histogenesis of these tumors has been much debated . due to their ultrastructural similarities with ependymal cells , they were initially thought to arise from ependymal cells , with reactive astrocytic proliferation . since immunohistochemical profile favors a glial origin , they were grouped with low - grade glial tumors . tanycytes were also proposed as source of origin , due to the presence of ultrastructural features of glial as well as ependymal components . however , the presence of round cells rather than spindle - shaped cells differentiates these lesions from tanycytic ependymomas . the identification of cells similar to subependymal glial precursor cells suggested alternate cell of origin . subependymal zone glial precursor cell origin can not explain the predominant peripheral and exophytic location of these lesions in spinal cord unlike their intracranial counterparts . the current concept seems to suggest that these progenitor cells exist throughout the spinal cord white matter as well as the root entry zones . they are more localized in the outer subpial white matter than the medial zones , especially at the dorsal and ventral spinocerebellar tracts . they tend to proliferate within their template zones and do not possess trans - zonal migratory ability . the tumor origin from these cells better explains the eccentric , subpial , and exophytic locations of spinal subependymomas . the progenitor cells origin postulated by horner et al is an alternative to the conventional old postnatal theory [ type 1 , figure 4 ] where the progenitor cells migrate from the subependymal zone to the outer zones . there are two alternative postulates : one where the stem cell divides asymmetrically and the daughter cell migrates to the outer white matter where it remains as a glial progenitor cell and multiplies [ type 2 , figure 4 ] , and the second which postulates that the stem cells exist separately in the outer zone where tracts are constantly proliferating even postnatally and these give rise progenitor glial cells [ type 3 , figure 4 ] . ( a ) post natal theory : where the subependymal stem cells give rise to glial progenitor cells which then migrate to the periphery . ( b and c ) alternate new theories where the stem cells themselves migrate to the periphery and become glial progenitor cells ( b ) or the stem cells already existing in the periphery of the cord become glial progenitor cells ( c ) . irrespective of their origin the subpial spinal white matter progenitor cells may be the origin of the spinal subependymoma . the subependymomas reported are more commonly located in the cervical cord and the cervico - thoracic cord followed by the pure thoracic and lumbar segments . one rare case occurring in the filum teminale has also been reported [ table 2 ] . radiologically , these lesions are located eccentrically within the cord , with iso or hypointense on t1-weighted images and mild hyperintensity on t2-weighted images . there is minimal diffuse or no enhancement on contrast.[148 ] these lesions can usually be excised totally . only three cases have been reported with recurrence of the tumor after initial total excision . all of them had a resurgery and were not subjected to adjuvant radiation or chemotherapy despite recurrence . the chances of recurrence after total excision are low ; hence , a total excision should always be attempted [ tables 1 and 2 ] . however , as with our case , the size of the lesion and its extensive intermingling with the nerve roots made it sometimes necessary to settle for a subtotal excision . there have been instances of postoperative radiation following subtotal excision , but it is generally not recommended . residual or recurrent tumor on follow up after gross total resection should be strongly considered for a re - excision rather than adjuvant therapy.[268 ]
subependymomas are extremely rare lesions of the spinal cord . 
 only 33 cases including ours have been reported in the cervical cord . 
 these are typically benign slow growing tumors occurring eccentrically within the cord , producing minimal neurological deficits . 
 the clinical , radiological , and histopathological aspects of this unusual lesion have been reviewed in detail . 
 as the histogenesis of this tumor is much debated , we propose an alternate origin for the same .