De Novo Renal Neoplasia After Kidney Transplantation According to New 2016 WHO Classification of Renal Tumors

BACKGROUND De novo renal neoplasia developing after kidney transplantation at Verona Kidney Transplant Center were reviewed according to new 2016 WHO Renal Tumor Classification. MATERIAL AND METHODS Primary renal tumors developed in native or transplanted kidneys de novo following renal transplantation were retrieved and histologically reviewed by three expert uropathologists. Immunoexpression of the diagnostic antigens CD13, CD10, CK7, CK34bE12, AMACR, CAIX, AE1/AE3, CK14, GATA-3, HMB-45, cathepsin-k, S100A1, and parvalbumin was assessed. Predictive antigens ph-mTOR and ph-p70S6k were also tested. RESULTS Two thousands and sixteen kidney transplantations have been carried out from 1968-2015. Follow-up was available per 1,646 patients (mean 8.4 years). We observed 16 cases of de novo renal neoplasia arising in patients 16 to 286 months post-transplantation. Nine clear cell, two papillary RCCs and a single case of the new WHO entity denominated "acquired cystic disease-associated RCC" were identified in native kidneys. Another new WHO tumor entity called "clear cell papillary RCC" was diagnosed and a new variant of papillary RCC with diffuse clear cytoplasm was also identified. The majority of tumors were low stage and low grade according to the new ISUP grading system. Seven patients were additionally treated with mTOR inhibitors. Post-cancer follow-up ranged from 62 to 281 months. One patient showed a recurrence (a lung metastases) and died. Of the remaining patients, three died of non-cancer-related causes. CONCLUSIONS The application of the new WHO 2016 classification has importance as it identifies new (18% of tumors) morphotypes that are likely to behave in a less aggressive fashion.