[A Case of de novo Neuroendocrine Prostate Cancer]

A 56-year-old man visited our hospital with a chief complaint of worsening urinary pain after a treatment by another doctor. Prostate specific antigen (PSA) was 429.66 ng/ml, and computed tomography (CT) revealed multiple lymph node enlargement and multiple bone metastases. Prostatic adenocarcinoma (Gleason score 4＋5) was detected on the first prostate biopsy. Based on these results, the clinical stage was determined to be cT4N1M1b Androgen deprivation therapy (ADT) was started, and PSA decreased to 0.03 ng/ml at 3 months, but micturition and perineal pain tended to worsen, and multiple liver metastases were confirmed on CT. The second biopsy examination was performed and a diagnosis of neuroendocrine prostate cancer (NEPC) was made. Chemotherapy for small cell lung cancer was immediately performed, but no response was seen, and he died 8 months after the first visit. Immunostaining of prostate tissue of the first biopsy revealed that de novo NEPC expressed both PSA and synaptophysin in tumor cells.