Prostate Lesion in an Adult

Specimen Type:

Prostate

History:

A 61-year- old men underwent radical prostatectomy for prostate cancer. Grossly, no identifiable tumor was readily appreciated. The specimen was submitted in its entirety.

Pathologic Features:

A small focus of typical prostatic adenocarcinoma was found in right peripheral zone, which is Gleason 4+4 ( Fig 1). In addition, on the left side, there is a florid proliferation of epithelium filling markedly dilated prostatic ducts ( Fig 2, 3). The epithelium is pseudostratified and shows a downward proliferation of anastomasing islands and trabeculae at various angles to the luminal surface ( Fig 4). Cystic spaces are formed within the epithelial islands and contain eosinophilic secretion (Fig 4). Papillary structures are appreciated in some areas ( Fig 5), and the proliferation shows a narrow stalk attached to the ducts (Fig 6). The cells display no significant cytologic atypia (Fig 7). The proliferative epithelium is strongly positive for CK7 ( Fig 8) while the superficial lining epithelium is positive for PAP focally. The lining cells of ducts are positive for PAP ( Fig 9). No definite continuity with urinary bladder or urethral margin is identified.

Differential Diagnosis:

  • Large prostatic polyp
  • Urothelial proliferation or urothelial metaplasia (fig 10)
  • Urothelial papilloma (fig 11)
  • Primary urothelial carcinoma or secondary carcinoma from urethra or bladder (Fig 12, 13)

Prostatic polyp: This polypoid or papillary lesion usually involves prostatic urethra, representing an exaggerated, proliferative expansion of prostatic epithelium into the prostatic urethra. The lining epithelium should be prostatic-type, which is positive for PAP, and negative for CK7. This benign lesion is uncommon, with about 200 cases reported in the literature, and patients usually present with hematuria.

Urothelial proliferation or urothelial metaplasia: This proliferative process occurring in the prostate ducts/acini are usually associated with chronic inflammation in the adjacent stroma. The proliferation is limited, and not complex in architecture.

Urothelial papilloma: Urothelial papilloma consists of papillae lined by less than 7 cells in thickness. Solid pattern with cystic spaces containing secretions is not an expected finding.

Primary urothelial carcinoma or secondary carcinoma from urethra or bladder: Cytologic atypia should be present to justify this diagnosis. Immunostain for PAP or PSA excludes poorly differentiated prostatic adenocarcinoma. Secondary cancer can be easily excluded clinically since it is virtually always clinically obvious when this cancer involves the prostate.

Diagnosis:

Inverted Papilloma arising from the Prostatic Ducts

Key Features:

  • The growth can be endophytic or exophytic
  • Downward proliferation of anastomasing islands and trabeculae
  • The epithelium is urothelial in nature, which is positive for high molecular weight cytokeratin
  • No cytologic atypia

The lesion consists of complex intraluminal growth of urothelium (positive for CK7) in prostatic duct (positive for PAP). The growth is characterized by a downward proliferation of anastomasing islands and trabeculae of urothelium at various angles to the luminal surface. There is no significant cytologic atypia. These features are diagnostic of inverted papilloma, similar to those seen in urinary tract. Urothelial neoplasm of prostate primary is rare, and the reported cases include urothelial carcinoma (reference 1) and urothelium carcinoma in situ. To our knowledge, inverted papilloma arising from the prostatic duct has not been reported in the literature. There are few reports of inverted papilloma arising from the prostatic urethra (reference 2).

References:

  1. Cheville JC, Dundore PA, Bostwick DG, Lieber MM, Batts KP, Sebo TJ, Farrow GM . Transitional cell carcinoma of the prostate: clinicopathologic study of 50 cases. Cancer. 1998 Feb 15;82(4):703-7.
  2. Vesa Llanes J, Domingo Ferrerons R, Muntane Hombrados MJ, Nadal Vidal C. Inverted papilloma of the prostatic urethra. Histopathogenetic considerations. Arch Esp Urol. 1994 Dec;47(10):1022-4.