A Multicenter Application of the 2018 Banff Classification for BK Polyomavirus-associated Nephropathy in Renal Transplantation.

BACKGROUND: With current immunosuppressive regimens, BK polyomavirus-associated nephropathy (BKPyVAN) is still a matter of concern. Stratification of patients at risk for allograft loss is of uttermost importance to guide treatment choice and assess prognosis. In 2018, the Banff working group proposed a classification scheme for the prognosis of BKPyVAN, but external application on independent cohorts is yet to be performed. We investigated how the 2018 Banff classification would perform in a multicenter cohort comprising 50 cases of biopsy-proven BKPyVAN compared to previously published classification systems. METHODS: We analyzed consecutive BKPyVAN cases from two Dutch university hospitals between 2002 and 2013, retrieved clinical data, and scored all biopsies according to the Banff 2018 classification, and as a comparison, 4 previously proposed BKPyVAN classification systems. We used estimated glomerular filtration rate trajectories and death-censored graft survival as primary endpoints. RESULTS: The 2018 Banff classification did not associate with estimated glomerular filtration rate decline or graft failure and performed only slightly better than the 4 previously proposed classifiers. Anti-human leukocyte antigen donor-specific antibodies (DSAs), especially in combination with ongoing biopsy-proven BKPyVAN on follow-up, did correlate with graft function and survival. Patients who were DSA+/BKPyVAN+ on follow-up had more inflammation at the baseline biopsy, which by itself was not associated with graft outcomes. CONCLUSIONS: Neither the 2018 Banff BKPyVAN classification nor previously published stratification systems could be applied to our multicenter patient cohort. Our data suggest that there might be a prognostic value for follow-up biopsies and DSA measurements to improve risk stratification after BKPyVAN, although prospective multicenter efforts with protocol measurements are needed to confirm this.

Merkel cell carcinoma: is this a true carcinoma?

Recent years have brought an enhanced understanding of Merkel cell carcinoma (MCC) biology, especially with regard to the Merkel cell polyoma virus as a causative agent. Differences between Merkel cell polyomavirus-positive and Merkel cell polyomavirus-negative MCC in morphology; gene expression, miRNA profiles and prognosis have been reported. Origin of MCC is controversial. Presence of neurosecretory granules has suggested that these carcinomas originate from one of the neurocrest derivatives, most probably Merkel cells; the name Merkel cell carcinoma is now widely accepted. Expression of PGP 9.5, chromogranin A and several neuropeptides, initially regarded as specific markers for neural and neuroendocrine cells, has recently been shown in a subset of lymphomas. MCC commonly expresses terminal deoxynucleotidyl transferase and PAX5. Their co-expression under physiologic circumstances is restricted to pro/pre-B cells and pre-B cells. These findings lead to the hypothesis by zur Hausen et al. that MCC originates from early B cells. This review was intended to critically appraise zur Hausen's hypothesis and discuss the possibility that MCC is a heterogenous entity with distinct subtypes.

Interobserver agreement for Polyomavirus nephropathy grading in renal allografts using the working proposal from the 10th Banff Conference on Allograft Pathology.

A classification schema for grading Polyomavirus nephropathy was proposed at the 2009 Banff allograft meeting. The schema included 3 stages of Polyomavirus nephropathy: early (stage A), florid (stage B), and late sclerosing (stage C). Grading categories for histologic viral load levels were also proposed. To examine the applicability and the interobserver agreement of the proposed Polyomavirus nephropathy grading schema, we evaluated 24 renal allograft biopsies with confirmed Polyomavirus nephropathy by histology and SV40. Four renal pathologists independently scored the Polyomavirus nephropathy stage (A, B, or C), without knowledge of the clinical history. Viral load was scored as a percent of tubules exhibiting viral replication, using either a 3-tier viral load score (1: ≤1%; 2: >1%-10%; 3: >10%) or a 4-tier score (1: ≤1%; 2: >1%-≤5%; 3: >5%-15%; 4: >15%). The κ score for the Polyomavirus nephropathy stage was 0.47 (95% confidence interval, 0.35-0.60; P < .001). There was a substantial agreement using both the 3-tier and the 4-tier scoring for the viral load (Kendall concordance coefficients, 0.72 and 0.76, respectively; P < .001 for both). A better complete agreement was found using the 3-tier viral load score. In this first attempt to evaluate the interobserver reproducibility of the proposed Polyomavirus nephropathy classifying schema, we demonstrated moderate κ agreement in assessing the Polyomavirus nephropathy stage and a substantial agreement in scoring the viral load level. The proposed grading schema can be applied in routine allograft biopsy practice for grading the Polyomavirus nephropathy stage and the viral load level.