[A Case of BRCA2 Mutation-Positive Intraductal Carcinoma of the Prostate].

A 75-year-old man presented with macroscopic hematuria and a high serum prostate-specific antigen (PSA) level. Macroscopic hematuria had subsided by the time of consultation. The PSA level was 38.590 ng/ml, which, along with rectal examination and magnetic resonance imaging findings, led to the suspicion of prostate cancer. Transrectal needle biopsy of the prostate revealed intraductal carcinoma of the prostate (IDC-P). Computed tomography and bone scintigraphy were performed, and the prostate cancer was classified as cT2cN0M0. After 6 months of combined androgen blockade therapy, a radical prostatectomy was performed; however, PSA levels continued to increase, and the patient was diagnosed with castration resistant prostate cancer. Multiple bone metastases appeared 5 months after the initiation of abiraterone therapy. Three courses of docetaxel and two courses of cabazitaxel were administered, but the disease progression continued. The IDC-P was found to be positive for the BRCA2 mutation by BRACAnalysis® performed at the start of cabazitaxel therapy. To our knowledge, no other cases of BRCA2 mutation positive IDC-P have been reported in Japan. After we started administration of Olaparib, the patient's PSA level was lowered and the disease progression stopped.