Banff 2024 Pancreas Transplantation Report: Diagnosis and impact of chronic active T cell-mediated allograft rejection and re-evaluation of the indeterminate category with utilization of leukocyte immunostains in biopsies with ambiguous findings

The current Banff report summarizes topics central to the pancreas session in the 2024 conference held in Paris (France). The focus of discussion was on diagnostic criteria of chronic active rejection, the indeterminate (IND) category, and the utility of immunostains in pancreas transplant biopsies. Concepts were validated in a retrospective PanTxBx cohort after the meeting. First, chronic active rejection criteria introduced in the 2022 report were confirmed, and recommendations were refined. The clinical relevance of this category, with an increased risk of graft loss, was proven in the retrospective cohort. Second, the so far very narrowly defined IND category was expanded from septal inflammation to also include subthreshold lobular changes and incomplete findings of antibody-mediated rejection. IND cases were evaluated in the context of the clinical findings and CD3 and CD68 immunostaining. This process helped in further subcategorizing the IND diagnoses into rejection and non-rejection events and, third, led to the general recommendations provided for utilization of CD3 and CD68 immunostains to facilitate the histologic diagnosis in unclear biopsies. The working group expects that the current recommendations and refinements will enhance the applicability and reproducibility of the histopathological pancreas schema. Additionally, an outlook is given regarding ongoing projects and future perspectives.