For dozens of years, a variety of pathological findings have been revealed 
through previous observations on surgically resected lesions from patients with 
intractable epilepsy, including excessive number of neurons in the molecular 
layer of cortices, unexpected existence of white matter neurons, and persistent 
columnar structure. These findings have sometimes been referred to as 
microdysgenesis (MD) or mild malformation of cortical development (mMCD), which 
is defined as microscopic abnormalities of brain formations with no 
macroscopical and neuroradiological findings. Taylor et al. (1971) described 
surgical cases with giant neurons and bizarre, grotesque cells as "focal 
dysplasia of the cerebral cortices with epilepsy." Since 1997, such 
malformations have subsequently been referred to as focal cortical dysplasia 
(FCD), in Greenfield's Neuropathology. Since early 2000, the definition of FCD 
has gradually been given a broader interpretation than the case described by 
Taylor et al., as shown in Palmini's classification (2004) or the newest 
classification (2011) proposed by the Neuropathology Task Force of the 
International League Against Epilepsy (ILAE). The ILAE classification describes 
3 types of disease: Type I, Type II, and Type III. Type I is equivalent to some, 
but not all, pathological phenotypes of MD or mMCD. Type II is Taylor's FCD 
alone. Type III, which was not included in Palmini's classification, merges 
brain malformation and other pathological findings. However, the reproducibility 
of pathological diagnosis by using the ILAE classification was low, except for 
Type IIb. Hence, future studies are necessary to provide further reliable 
criteria for the pathological diagnosis of epilepsy patients.