Polyomavirus nephropathy - recent pathological diagnostic problems and the report from the 2011 Banff meeting.

Polyomavirus nephropathy (PVN) is a cause of renal allograft dysfunction. Early detection of pathological abnormalities is not easy even in cases with urine decoy cells or polyomavirus viremia. A pathological classification for PVN was proposed by the Banff PVN working group, although the availability of the proposed schema has not been extensively evaluated in the clinical field. At the Banff meeting in 2011, the PVN working group reported the results of the evaluation on interobserver reproducibility and a clinicopathological study of PVN stages and renal outcome. Fair or good reproducibility was noted, although the PVN classification required further modification.