Redefining a Rare CNS Tumour Through Targeted Genetic Sequencing

Abstract

Abstract AIMS Isolated cerebellar vermis lesions in adults is a rare location and entity with few literature case reports detailing gangliogliomas and gangliocytomas. Using targeted genetic sequencing, traditional histological diagnosis can be refined further, with a clear impact on prognosis as well as possible genetic counselling implications. METHOD A single case of cerebellar vermis lesion, identified incidentally through imaging of a neck nodule, with subtle features of ataxia and mild impairment of initiation of speech. Sub-total resection of lesion underwent standard histopathological work-up, followed by targeted genetic sequencing to obtain an integrated diagnosis. RESULTS Histological assessment identified atypical ganglion cells labelled with Synaptophysin on immunohistochemistry. Features closely resembled dysplastic cerebellar gangliocytoma (Lhermitte-Duclos Disease). Further targeted sequencing showed no evidence of IDH1, IDH2, TERT promoter, or histone mutation, however, BRAF mutation was present, supporting an alternate diagnosis of ganglioglioma. CONCLUSION Precision medicine is facilitated with advanced diagnostic techniques. This redefines categorisation of some CNS tumours, particularly rare entities. Techniques are especially valuable to individual patient management as they can have a direct impact on aspects of clinical work-up, prognosis, follow-up, and in some cases, genetic counselling.