Although several models have been developed to predict the probability of Gleason sum upgrading between biopsy and radical prostatectomy specimens,most of these models are restricted to prostatespecific antigen screening-detected prostate cancer.This study aimed to build a nomogram for the prediction of Gleason sum upgrading in clinically diagnosed prostate cancer.The study cohort comprised 269 Chinese prostate cancer patients who underwent prostate biopsy with a minimum of 10 cores and were subsequently treated with radical prostatectomy.Of all included patients,220(81.8%) were referred with clinical symptoms.The prostate-specific antigen level,primary and secondary biopsy Gleason scores,and clinical T category were used in a multivariate logistic regression model to predict the probability of Gleason sum upgrading.The developed nomogram was validated internally.Gleason sum upgrading was observed in 90(33.5%) patients.Our nomogram showed a bootstrap-corrected concordance index of 0.789 and good calibration using 4 readily available variables.The nomogram also demonstrated satisfactory statistical performance for predicting significant upgrading.External validation of the nomogram published by Chun et al.in our cohort showed a marked discordance between the observed and predicted probabilities of Gleason sum upgrading.In summary,a new nomogram to predict Gleason sum upgrading in clinically diagnosed prostate cancer was developed,and it demonstrated good statistical performance upon internal validation. Although several models have been developed to predict the probability of Gleason sum upgrading between biopsy and radical prostatectomy specimens, most of these models are restricted to prostatespecific antigen screening-detected prostate cancer. This study aimed to build a nomogram for the prediction of Gleason sum upgrading in clinically diagnosed prostate cancer. The study cohort comprised 269 Chinese prostate cancer patients under underwent biopsy with a minimum of 10 cores and were subsequently treated with radical prostatectomy. All were included patients, 220 (81.8%) were referred with clinical symptoms. prostate-specific antigen level, primary and secondary biopsy Gleason scores, and clinical T category were used in a multivariate logistic regression model to predict the probability of Gleason sum upgrading. The developed nomogram was validated internally. Gleason sum upgrading was observed in 90 (33.5 %) patients.Our nomogram showed a bootstrap-corrected concordance index of 0.78 9 and good calibration using 4 well available variables. Nomogram also demonstrated satisfactory statistical performance for predicting significant upgrading. External validation of the nomogram published by Chun et al. In our cohort showed a marked discordance between the observed and predicted probabilities of Gleason sum upgrading .In summary, a new nomogram to predict Gleason sum upgrading in clinically diagnosed prostate cancer was developed, and it demonstrated good statistical performance upon internal validation.