Characterization of prostate cancer incidentally detected in radical cystoprostatectomy specimens from Japanese men with bladder cancer

The objective of this study was to investigate and characterize the clinicopathological features of incidentally detected prostate cancer in radical cystoprostatectomy specimens from Japanese men with bladder cancer. We reviewed the pathological reports of 251 male patients who underwent radical cystoprostatectomy for bladder cancer at our institution and identified men with incidentally detected prostate cancer in these specimens. Clinicopathological data of patients with incidental prostate cancer in cystoprostatectomy specimens (group A) were compared with those of 193 patients with clinically detected prostate cancer who underwent radical prostatectomy (group B). Immunohistochemical staining was also performed to measure the expression levels of Ki-67, p53 and androgen receptor (AR) proteins in specimens from both groups A and B. In this series, a total of 31 patients (12.3%; group A) were incidentally diagnosed as having prostate cancer in radical cystoprostatectomy specimens. Clinically significant cancer, defined as any tumor greater than 0.5 cc according to the report by Stamy et al. (Cancer 71:933-938, 1993) was detected in 9 (29.0%) in group A and 170 (88.1%) in group B. Mean age in group A was significantly older than that in group B, while despite the lack of significant difference in the incidence of seminal vesicle invasion between these two groups, other parameters in group A were significantly more favorable than those in group B, including serum prostate-specific antigen, pathological stage, Gleason score, perineural invasion and capsular penetration. None of the patients in group A had biochemical recurrence (median observation period, 82 months); however, biochemical recurrence occurred in 41 (21.2%) in group B (median observation period, 46 months). Furthermore, immunohistochemical study demonstrated the significantly greater expression of Ki-67, p53 and AR proteins in group B than in group A. Clinicopathological features of incidentally detected prostate cancer are markedly more favorable than those of clinically detected prostate cancer, which may reflect less aggressive biological phenotypes of incidental prostate cancer arising in Japanese men.