Figure 14. Banff Lesion Score cg (GBM double contours). This score represents the presence and extent of GBM double contours, a criterion for Chronic Active AMR. The score ranges from 0 to 3 and is based on the percentage of capillary loops with double contours as evident on EM (Banff Lesion Score cg1a) or LM (cg1b to cg3) in the most severely affected glomerulus. A, cg1a—GBM with double contours (short black arrows point to areas of original basement membrane and red arrows point to areas of new basement membrane formation), visible by EM only. Double contours, such as those noted in this image must be accompanied by endothelial cell swelling (long black arrow) and/or subendothelial widening and must involve at least 3 glomerular capillaries by EM for a Score of cg1a. Scores of greater than cg1a are based on light microscopic appearance which can best be examined by silver stains. Transmission EM, original magnification x8,000. B, Banff Lesion Score cg1b—double contours (arrow) identified on LM which involve up to 25% of the capillary loops of this most affected glomerulus. Jones silver stain, original magnification x400. C, Banff Lesion Score cg2—double contours (arrows) present in 26-50% of this most affected glomerulus; Jones silver stain, original magnification x400. D, Banff Lesion Score cg3—double contours (arrows) present in >50% of this most affected glomerulus. Jones silver stain, original magnification x400.