Florid hyperplasia of mesonephric remnants involving prostate and periprostatic tissue. Possible confusion with...

Two cases of florid hyperplasia of mesonephric remnants occurring in the prostate are described. One case was originally interpreted as invasive adenocarcinoma on transurethral resection (TUR), resulting in radical prostatectomy. In the second case, a TUR specimen was diagnostic for adenocarcinoma, which was confirmed in the radical prostatectomy specimen. Florid mesonephric hyperplasia in the second case was an incidental finding. The TUR specimen in the first case and sections of the prostatectomy specimens in both cases contained a proliferation of tubules, which ranged from aggregates of microacini to dilated structures containing a characteristic colloid-like material. The location of these lesions in the base of the prostate gland and periprostatic soft tissue suggests that these may be mesonephric remnants that have become hyperplastic. This type of lesion shares many features with mesonephric hyperplasia occurring in the female genital tract, including the presence of eosinophilic intratubular material and a lobular arrangement of microacini lined by a single layer of epithelium with prominent nucleoli. However, the latter feature, along with the apparent permeation of the prostatic fibromuscular stroma, periprostatic soft tissue, and even neural spaces, closely mimicked prostatic adenocarcinoma. In both cases, the proliferating tubules reacted with keratin 903 and were negative for prostate-specific antigen and prostate acid phosphatase, thereby excluding the diagnosis of prostatic adenocarcinoma. We concluded that lobular hyperplasia of mesonephric remnants is a distinct histologic entity that may occur in the prostate and periprostatic soft tissues and closely mimic prostatic adenocarcinoma.