A 74-year-old man who was married with a son and daughter was admitted because of intermittent mucoid discharge from his urethra and difficulty voiding for 3 years. Indwelling catheterization was performed because of urinary retention. Digital rectal exanmination revealed a suspicious soft cystic mass with an unclear boundary in the upper left area of the moderately enlarged prostate. Serum prostate-specific antigen (PSA) was 4.12 ng/ml. Imaging studies (Figure 1) and an endoscopic examination (Figure 2) were subsequently performed. Magnetic resonance imaging (MRI) detected an irregular cystic-solid mass with villiform long T1 and T2 signals in the left ejaculatory duct area. Vasography showed an incomplete cyst-like structure with a filling defect under the bladder. Cystoscopy disclosed a cystic cavity filled with mucoid substance and multiple papillary neoplasms, which opened into the prostatic urethra near the top of the verumontanum. The cystoscope could be inserted into the right seminal vesicle through the urethral opening. Biopsies showed that the neoplasm was a metastatic mucinous adenocarcinoma or tubulo-villous adenoma. Immunohistochemistry revealed it to be a mucinous adenocarcinoma. All gastrointestinal tract tumor markers were normal. Computed tomography (CT) scanning showed a cystic-solid mass occupying the left ejaculatory duct area without renal agenesis. Contrast agent revealed an obviously enhanced cyst wall and a papillary lesion at the junction of the sigmoid colon and rectum. Colonoscopy revealed a 2.0-cm polypoid mass in the proximal rectum. An endoscopic polypectomy was performed and the pathological result was a tubulo-villous adenoma. A radical prostatectomy and seminal vesiculectomy were then performed. The pathological diagnosis was adenocarcinoma with 55% mucinous adenocarcinoma (enteric-type). No lipochrome pigment granules were oberved in the tumor. Immunohistochemistry showed PSA (-), P504S (+), 34betaE12 (+/-), P63 (-), ERG (-), CK7 (+), CK20 (+), CDX-2 (3+), SATB-2 (-), CEA (-), AR (-), Ki-67 (40%+), PAX2 (-), PAX8 (-) and MUC6 (2%+) (Figure 3).