[A case of prostate cancer with cyst formation].

We treated a case of prostate cancer with cyst formation in an 80-year-old Japanese man presenting with constipation. Fist-sized elastic soft mass was palpable by digital rectal examination. Computed tomography and magnetic resonance imaging demonstrated a retrovesical cystic mass arisen from the prostate. Serum prostate-specific antigen (PSA) was elevated to 15.7 ng/ml. Transrectal prostate needle biopsy revealed moderately differentiated adenocarcinoma and puncture of the cyst yielded aseptic bloody fluid. With a clinical diagnosis of prostate cancer (T2b N0 M1b) with cystic formation, hormonal therapy with a luteinizing hormone releasing hormone analogue and bicalutamide significantly lowered the serum PSA level. One year later, the cyst was reduced in volume and constipation had resolved. A total of 57 cases of prostate cancer with cyst formation are reviewed.