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Although the posterior fossa is a common location for paediatric brain tumours [1], diffuse glioma isolated to the cerebellum is an extremely rare imaging entity. Only two cases of isolated diffuse paediatric cerebellar glioma have been reported in the English language to the best of our knowledge [2, 3], and only one of these cases had a similar imaging phenotype to our cases [3]. Although somewhat similar to Lhermitte-Duclos (dysplastic gangliocytoma of the cerebellum), the appearances are distinct from other neoplastic entities of the paediatric posterior fossa. Clinical presentation and neurological examination findings are vital however to help differentiate other diffuse pathologies involving the cerebellum such as rhombencephalitis. Presented here are two diffuse cerebellar gliomas in children under the age of 3 with near identical imaging phenotypes demonstrating differing histological and molecular genetic profiles., (© 2023. Crown.)

Background: Lhermitte-Duclos disease (LDD; dysplastic gangliocytoma of the cerebellum) is a rare hamartoma of the cerebellum. It was first described by Lhermitte and Duclos in 1920 as "Sur un ganglioneurome diffus du cortex du cervelet" (Lhermitte and Duclos [Bull Assoc Fr Etude Cancer 9:99-107, 1920]). Since then, due to its rarity and the variability of its presentation, the diagnosis is often missed. It is not only important for the neurosurgeon and the pathologist to be aware of this entity so as to differentiate from malignant lesions but also to distinguish it from other cerebellar malformations, which may be hypoplastic or dysplastic, focal or diffuse in nature, with brain stem and cerebral involvement, and varied natural course., Illustrative Case: We report a case of LDD in a 16-year-old boy. This case exemplifies the rarity of the disease leading to lack of awareness with which the diagnosis was easily missed. We also take this opportunity to discuss the clinical presentation, neuroradiological appearance, and a brief summary of histopathological findings, pathogenetic considerations, and neurogenetical aspects.