English: Macroscopical and histological features of microlissencephaly in a 27 WG foetus (LIS_TUB_009_fœtus19) with TUBB2B mutation. Macroscopical view of the left hemisphere displaying agyria with absent sylvian fissure absent olfactory bulbs (a); absent olfactory bulbs severely hypoplastic brainstem and cerebellum (b). Coronal section passing through the hemispheres displaying a thin mantle with absent corpus callosum, internal capsule and basal ganglia, along with enlarged ventricles and voluminous germinal zones (c), diffuse disorganization of the cortical plate with massive overmigration of cells within the meningeal spaces (d), with at higher magnification a cobblestone pattern with numerous tortuous vessels (e), thickened meninges containing diffuse overmigration foci at all levels of the brainstem, which is unusually flat, with absent pontine nuclei (arrow) and olivary nuclei (asterisk) (f), disorganized cerebellar cortex cytoarchitecture due to abnormal migration of granule cells in the meninges leading to a fusion of folia identical to what observed in “cobblestone” dysplasia (g) (Scale bars: a: 2 mm, b: 100 μm, c, d: 50 μm, e: 1 mm, f: 10 μm).