Figure 9. Banff Lesion Scores for ct (tubular atrophy) and ci (interstitial fibrosis). The ci and ct Scores are both based on calculating the total percentage of cortex involved and require a diligent assessment of all foci of ct and ci as this process is often multifocal; ct and ci scores may not always be equally advanced. A, This image demonstrates an area of non-atrophic tubules (long arrow), compared to an area of tubular atrophy (short arrow) without an obvious increase in interstitial fibrosis. PAS, original magnification x200. There are different morphological types of tubular atrophy with differing appearances, including conventional, thyroidization, and endocrine-like types. B, Tubular atrophy of conventional type with interstitial fibrosis. Tubular areas are separated by areas of interstitial fibrosis and tubules show thickened basement membranes and > 50% reduction in tubular diameter (long arrows). PAS, original magnification x200. C, Thyroidization type atrophy. Here, tubules appear dilated, have flattened epithelial cells, and contain eosinophilic and brightly periodic-acid-Schiff-positive uromodulin casts (long arrow). PAS, original magnification x200. D, endocrine-like type, characterized by shrunken tubules with cuboidal epithelium and “tubular simplification” (long arrow). Compared with the other types of tubular atrophy, endocrine-like type does not have thickened basement membranes but still counts toward the ct score. PAS, original magnification x400.