The tubules show diffuse simplification, suggestive of acute tubular injury or acute tubular necrosis (or ATN-like changes). Coupled with focal positivity of C4d in the peritubular capillaries, these changes could be interpreted as acute antibody-mediated rejection, type 1. Of course, for a difinitive diagnosis of acute antibody-mediated rejection, patient must also have renal dysfunction and positive donor specific antibody.

The arterial intima appears thickened, probably due to edema (as part of acute antibody-mediated rejection?), or intimal fibrotic thickening as part of donor's disease.

Thank you, frankbj, for posting this interesting case. After more discussion or comments, please let us know your diagnosis.