[Neuroendocrine Differentiation of Prostate Cancer : A Case Report].

A 79-year-old man underwent a transrectal prostate needle biopsy with a prostate-specific antigen (PSA) level of 12.0 ng/ml. He was diagnosed with adenocarcinoma (Gleason score 4＋3, cT3aN0M0) and underwent radiation therapy. Eight months later, he was administered hormone therapy because of a rise in PSA level to 8.4 ng/ml. One year and 5 months later, he experienced back pain, and computed tomography revealed multiple lymphadenopathies and irregular prostate enlargement. The PSA level was 0.097 ng/ml. Re-biopsy of the prostate and biopsy of the lymph node were performed. Pathological examination revealed neuroendocrine differentiation of the prostate. The disease progressed rapidly, and the patient died 4 months after the biopsy. Neuroendocrine differentiation of prostate cancer is rare, and its development may not be consistent with PSA levels. Therefore, periodic imaging examinations should be conducted, even when PSA levels are low.