Peritoneal invasion of prostate cancer directly confirmed during robot‐assisted radical prostatectomy

INTRODUCTION: Several studies have been published on direct rectal invasion in patients with advanced metastatic prostate cancer, but few have directly confirmed intraoperative invasion of prostate cancer into the peritoneum. CASE PRESENTATION: We report the case of a 73‐year‐old man with prostate cancer who exhibited peritoneal invasion during robot‐assisted radical prostatectomy. His prostate‐specific antigen level fell to 0.38 ng/mL after surgery; he was therefore prescribed radiation and androgen‐deprivation therapies that controlled the cancer for more than 1 year. CONCLUSIONS: We encountered a case showing direct peritoneal invasion of prostate cancer during robot‐assisted radical prostatectomy. If invasion of the seminal vesicle is suspected, the vesicorectal fossa should be examined during robot‐assisted radical prostatectomy. Preoperative confirmation by diffusion magnetic resonance imaging of the peritoneum is also useful.