Abstracts

The spectrum of glioneuronal lesions underlying intractable epilepsies includes malformative pathologies like focal cortical dysplasia (FCD); and neoplastic lesions like gangliogliomas (GG) and dysembryoplastic neuroepithelial tumours (DNET). These glioneuronal lesions may occur either singly or as dual lesions having the presence of both malformative and neoplastic elements simultaneously. However, lacunae in knowledge exist in terms of the relationship between the malformative and neoplastic glioneuronal lesions. Recently CD34, a stem cell marker transiently expressed during early neuralation, has been identified in these tumours. We undertook this study to (i) evaluate the role of CD 34 as a diagnostic marker for glioneuronal lesions of epilepsy (GG, DNET and FCD), and (ii) to attempt to define the relationship and origin of various glioneuronal lesions associated with epilepsy, using CD 34 as a marker. In the present study, we have examined tissue resected from twenty-six (n=26) patients with medically intractable epilepsy associated with glioneuronal lesions (GG, DNET and CD). Immunohistochemical (IHC) staining was done with antibodies against CD34 antigen. Dysplastic neurons, which could not be identified on routine haematoxylin and eosin (HandE) staining, were highlighted by CD 34-immunostaining. FCDs showed solitary or small clusters of CD34-immunoreactive cells in 40% cases (2 out of 5). While isolated GGs showed immunoreactivity for CD 34 in only 25% (1 out of 4) cases, prominent immunoreactivity was observed in dual lesions (GG with FCD), with 80% (8 out of 10) cases showing positivity in GG areas and all 10 cases showing positivity in FCD areas. However, cases of DNET were largely negative for CD 34-immunoreactive cells, with only 33% (1out of 3) cases of dual lesions (DNET with FCD) showing positivity in the FCD areas. None of the adult control tissues and none of the specimen obtained from the developing brain, contained CD34-immunoreactive neural cells. CD34 may, thus, represent a valuable marker for the diagnostic evaluation of neoplastic and / or malformative pathological changes in intractable epilepsy patients. The CD34 immunoreactivity of these lesions indicates an origin from dysplastic or undifferentiated neural precursors. Based on these findings, we propose a common origin of GG and FCD, from a bipotent precursor that undergoes abnormal glioneuronal development, while the cases of DNET possibly have a different origin.