Evolution of the Banff Working Classification of Renal Allograft Pathology: Updates and Future Directions

Abstract

One of the important challenges after renal transplantation is the accurate identification and appropriate management of the graft dysfunction [2,3]. The causes of dysfunction vary depending on many factors, including the time post-transplant, type of immunosuppression used, living vs. cadaveric origin of the organ, and so on [4]. These often require recourse to the invasive procedure of renal allograft biopsy, which is still the gold standard test for an accurate diagnosis and categorization of rejection, for example [3]. The safety and clinical utility of the biopsy has been proved beyond doubt in numerous clinical studies during the last few decades [5][6][7][8][9][10][11]. However, the pathological interpretation of the biopsies is a daunting task and fraught with interobserver variation. Moreover, the pathology of transplantation is continuously evolving [12][13][14][15][16][17]. The Banff classification was introduced to address the above issues in the reporting of renal transplant pathology and to harmonize the reporting of the lesions in a uniform language, which is understood by the clinicians, pathologists, basic scientists and transplant surgeons alike [12,17]. The first meeting of the Banff group took place in 1991 at Banff, Canada and the first detailed publication appeared in 1993 [12,15,17]. Since then, regular meetings of the ever expanding group have been held every two years with timely updates, additions and revisions of the original classification. The aim of these meetings has been to revisit and refine the original classification in the light of accumulating new research and evidence from ongoing studies [12,[17][18][19]. Regarding individual diagnostic categories, major changes have occurred in the categories of antibody-mediated rejection, T-CellMediated Rejection (TCMR) and chronic allograft changes. Some of these evolutionary changes in the diagnostic approach have been reviewed in detail by this author elsewhere [13]. Briefly, the most spectacular changes have taken place in the category of ABMR [13]. The detailed pathology-based diagnostic criteria have been devised and updated for an accurate diagnosis and categorization of ABMR into acute and chronic active categories. The major impetus for this surge in interest in ABMR has been provided by the discovery and the widespread use of c4d as a biomarker for ABMR [20][21][22]. A subtype of ABMR, c4d-negative ABMR has been recognized and a Banff Working Group established to devise the evidence-based criteria of this subtype and to determine the full impact of allo-antibodies on the kidney allograft. A correlation has been found between ABMR diagnosed by histological criteria and molecular profiling. Further work is needed before these diagnostic modalities are merged smoothly into a workable classification [23][24][25][26][27][28]. AbstractRenal transplant pathology is a complex and rapidly evolving field of surgical pathology and the pathologic interpretation of renal allograft biopsy pose significant challenges and opportunities to the ...

Revisiting IF/TA Category of Banff Working Classification of Renal Allograft Pathology: Have the Objectives been Achieved?

“…Interstitial Fibrosis/Tubular Atrophy (IF/TA) is, like its predecessor of Chronic Allograft Nephropathy (CAN), a purely descriptive designation depicting the micro-scopical appearances of chronic fibrosing lesions observed on renal allograft biopsies typically in the setting of chronic allograft dysfunction [1,2]. However, subclinical forms of IF/TA are also commonly observed on the protocol biopsies in well-functioning renal allografts [3][4][5].…”

“…However, subclinical forms of IF/TA are also commonly observed on the protocol biopsies in well-functioning renal allografts [3][4][5]. The term was introduced by the Banff classification in its 2005 meeting as a replacement for the then popular category 5 of the Banff classification, i.e., the CAN [1,6]. The aim was to encourage the transplant pathologists to look for and identify the specific causes of late allograft dysfunction on renal allograft biopsies and not just simply dump all the chronic transplant lesions into the paper wastebasket category of CAN, so as to guide optimal patient management.…”

“…But apparently, little attempt was made in real practice by the reporting pathologists in sub-classifying CAN and assigning the proper etiological designation to individual cases. Moreover, the widespread use of the term of CAN led to misconception in the minds of many that it is a specific disease entity [1,2,6]. This prompted the Banff group to modify the nomenclature of this category and this lesion dominated the agenda of Banff 2005 meeting.…”