Histopathological assessment of the microscopic activity in inflammatory bowel diseases: What are we looking for?

Table 4 Nancy histological index

Grade	Criteria
Grade 0 (no histological significant disease)	No or mild increase in chronic inflammatory infiltrate
Grade 1 (chronic inflammatory infiltrate with no acute inflammatory infiltrate)	Moderate or marked increase in chronic inflammatory infiltrate that is easily apparent. No acute inflammatory infiltrate is present
Grade 2 (mildly active disease)	Few or rare neutrophils in lamina propria or in the epithelium that are difficult to see
Grade 3 (moderately active disease)	Presence of multiple clusters of neutrophils in lamina propria and/or in epithelium that are easily apparent
Grade 4 (severely active disease)	Loss of colonic crypts replaced with “immature” granulation tissue (disorganized blood vessels with extravasated neutrophils) or the presence of fibrinopurulent exudate