[Carcinoma in situ of the bladder involving the prostate with an unusual invasive pattern following BCG therapy: a case report].

We report a case of carcinoma in situ (CIS) of the bladder involving the prostate with an unusual invasive pattern following Bacillus Calmette Guerin (BCG) therapy. A 41-year-old man achieved complete response after a course of intravesical instillation of BCG for diffuse CIS of the bladder. Two years later, urine cytology became positive. We performed random biopsy of the bladder and urethra three times and examined the bilateral upper urinary tract with retrograde pyelography and split urine cytology. However, none of these examinations revealed any malignant features, leading to a suspicion that the prostate was the recurrent site. Transrectal needle biopsy of the prostate revealed urothelial carcinoma (UC) at the transition between bladder and prostate. Transurethral biopsy of the prostatic urethra also detected UC in a core of the bladder neck only. Under a diagnosis of UC involving the prostate, we performed total cystectomy with ileal conduit diversion. Histopathological findings of the surgical specimen showed prostatic stromal invasion of the tumor. In this case, CIS at the bladder neck might directly and silently invade the prostatic stroma, thus transurethral biopsy contributed little to the diganosis. We recommend transrectal needle biopsy of the prostate as well as TUR biopsy in such rare cases.