Pure ductal adenocarcinoma of the prostate protruding into the prostatic urethra: A case report of MRI findings and literature review.

Ductal adenocarcinoma of the prostate (DCa) is the histological variant of prostatic carcinoma. The macroscopic finding of DCa arising from primary duct by urethroscopy is papillary excrescences in the prostatic urethra. But the finding of MRI remains poorly understood, since there is no coherent report on the MRI finding of DCa arising from primary duct. We herein report a case of DCa arising from primary duct and forming papillary excrescences in the prostatic urethra. The patient was a male in his 70s and presented with gross hematuria a few days ago. Blood test showed elevated prostate specific antigen (PSA). Prostate MRI was performed. There were two lesions in the prostatic urethra and the right transition zone (TZ). On T 2-weighted image (T2WI), the lesion in the prostatic urethra was identifiable, but the lesion in the right TZ was difficult to identify. On diffusion-weighted image (DWI), both lesions showed hyperintense signal and could be identified, and there was continuity between them. Urethroscopy was performed, there was the lesion with papillary excrescences developing from the right dorsal side of prostatic urethra. Transurethral resection of the prostate was performed. The pathological diagnosis was DCa (pure type). A review of previous literature showed that DCa had a slightly hypointense signal on T2WI. It may be difficult to identify DCa in the TZ because DCa and the TZ show similar signals on T2WI. DWI may be useful to accurately assess DCa arising from primary duct.