Granular swollen epithelial cells in the kidney allograft: A clinicopathological study with special emphasis on possible marker for kidney allograft aging

Abstract

Aim: To elucidate the clinicopathological significance of granular swollen epithelial cells (GSECs), which provides histological evidence in the diagnosis of mitochondrial nephropathy, but incidentally observed in renal allografts, we evaluated GSECs as a surrogate histological marker for kidney allograft aging, as previously reported for p16, p21, and β-galactosidase. Methods: We retrospectively reviewed 426 kidney allograft biopsy specimens diagnosed at our university from January 2009 to April 2015. The prevalence and density of GSECs were compared with an age-matched control group of 508 native kidney biopsies. GSECs were defined as swollen (>2 times larger than normal renal tubular cells) epithelial cells best observed using Masson trichrome staining. Morphometric analyses were performed using digital microscopy software. Results: The prevalence of GSECs was 7.7% in allograft kidneys and 8.1% in native kidneys. GSECs in kidney allografts were predominantly detected in medullary renal tubules, but not in the Bowman's capsular epithelium or podocytes. GSECs were observed in the following cases; no remarkable changes, n = 11; interstitial fibrosis and tubular atrophy, n = 7; chronic calcineurin inhibitor toxicity, n = 5; antibody-mediated rejection, n = 3; T cell-mediated rejection grade IA, n = 1; and others, n = 6. Compared with control specimens, medullary density of GSECs in kidney allografts was significantly increased. The prevalence of GSECs slightly increased with post-transplant duration; however, this trend was not statistically significant. Conclusions: The present study does not provide pathological significance of GSEC in kidney allografts in terms of allograft aging, and warrant the further research with molecular approach.