Assessment of adult renal cell carcinoma types presenting to a tertiary care hospital in Sri Lanka and the intraobserver variability of two nuclear grading systems for clear cell renal cell carcinoma

: The histomorphology remains the foundation in classification of renal cell carcinoma (RCC). The nuclear grading is significant in prognostication of certain subtypes for which Fuhrman system was used before the introduction of WHO/ISUP system in 2012. : To describe types of adult RCC presenting to a tertiary care hospital in Sri Lanka and to assess intraobserver variability of two nuclear grading systems for clear cell RCC. : One representative H and E stained slide from all RCC reported in National Hospital of Sri Lanka and University of Colombo, Sri Lanka from 2016-2020 were selected (n = 228). Tumours were classified by morphology according to WHO-5th series. Two rounds each of nuclear grade assessment using Fuhrman and WHO/ISUP systems were performed on clear cell RCC (n = 189) to calculate intraobserver agreement using kappa index (SPSS 25.0). Of the 228 cases 189 were of clear cell (82.9%), 24 were papillary (10.5%) and 6 were chromophobe (2.6%). Seven were identified requiring molecular testing for accurate diagnosis (3.1%). Kappa value was 0.953 for WHO/ISUP (95% confidence interval 0.916 – 0.99) and 0.856 for Fuhrman system (95% confidence interval 0.794 – 0.918). Majority of the RCC were clear cell, followed by papillary and chromophobe. Other subtypes were rare. A few required molecular testing for diagnosis. WHO/ISUP system showed an almost perfect level of intraobserver agreement. Although discordant with many studies, Fuhrman system also demonstrated a strong level of intraobserver agreement.