Hyperplasia of Prostatic Mesonephric Remnants: A Potential Pitfall in the Evaluation of Prostate Gland Biopsy

Abstract

A case of hyperplasia of mesonephric remnants involving the prostate gland is described. The patient underwent prostatic transurethral resection for symptoms of prostatism secondary to nodular hyperplasia. Mesonephric hyperplasia, predominantly in the bladder neck, was an incidental finding. The lesion is a distinct histological entity that closely mimics prostatic adendoma.' This type of lesion shares many features with mesonephric hyperplasia in the uterine cervix, which can be confuaed with cervical adenocarcinoma.23 The presence of mimacini lined by 1 layer of attenuated flattened epithelial cells without anaplasia that sometimes contain colloid-like material in the lumen should alert one to the possibility of mesonephric hyperplasia and, thus, lead to immunohistochemical studies. Prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) yield negative results by immunohistochemical technique. CASE REPORT A 66year-old white man presented with sporadic hematuria 2 months in duration. He had undergone suprapubic prostatectomy for nodular hyperplasia elsewhere 5 years previously. Rectal examination revealed a hard middle lobe that was suspicious for adenocarcinoma. Cystoscopy showed retraction of the bladder neck and a purpuric area of the mucosa. hurethral resection of the prostate was performed and 12 gm. of tissue were resected. The prostatic chips were embedded for histological examination, resulting in 9 slides containing 167 fragments. The transurethral resection specimen revealed nodular prostatic hyperplasia due to the proliferation of ducts and acini, smooth muscle cells and fibroblasts in variable proportions. Two fragments contained a florid proliferation of tubules or acini closely arranged, or dispersed, isolated and haphazardly distributed in the stroma with an infiltrative pattern (part A of figure). Proliferation predominated into the bladder neck. The tubules or acini were lined by 1 layer of cuboidal cells with round to slightly ovoid, relatively bland nuclei without prominent nucleoli or significant epithelial atypia (part B of figure). These cells had scanty, pale pink rather than abundant pale cytoplasm. Ciliated or hobnailed cells were not noted and cell borders were indistinct. There were no bizarre, complex glandular configurations or pointed edge acini. Some tubules contained dense colloid-like secretory material in the lumen (part C of figure). Inflammation and necrosis were absent. The intraluminal content of the tubules or acini was periodic acid, SchSpositive. Immunohistochemid studies for PSA, PAP, Enzo-keratin 903 (clone 348312), Dako-cytokeratin 348312, carcinoembryonic antigen, chromogranin A, serotonin, synaptophysin and neuron-specific enolase were negative, and controls were positive. The slides from the pathological study of the previous suprapubic prostatectomy were reviewed and did not reveal proliferation of mesonephric remnants concomitant with nodular hyperplasia. DISCUSSION The mesonephric or woman ducts develop into the efferent ducts of the testis and the epidid-des, vasa deferentia, seminal vesicles and ejaculatory ducts. Estimates of the frequency of persistence of mesonephric duct remnants in the prostate gland are unknown. The predominant proliferation of mesonephric foci into the bladder neck in our case suggests that the lesion may have originated in the area of the embryological mesonepbric duct. Persistent mesonephric remnants in this region could explain the concentration of mesonephric hyperplasia in the area. Our case had a striking proliferation of small tubules with