In a pathological examination of renal biopsy specimen, focal change is diagnosed when the changes are limited to:

Renal biopsy specimen assessment: Each region of a renal biopsy is assessed. <50% involvement is considered focal, and >50% is diffuse. Injury in each glomerular tuft can be segmental or global. Glomeruli having proliferative characteristics. When cells in the capillary tuft proliferate, it is called endocapillary, and if extends into Bowman's space, it is called extracapillary. Ref: Harrison-18, P-2339.