[775] Mesonephric Remnant Hyperplasia Involving the Prostate and Periprostatic Tissue: Findings at Radical Prostatectomy (RP).

Ying-Bei Chen, Samson Fine, Jonathan I Epstein. Memorial Sloan-Kettering Cancer Center, New York; The Johns Hopkins Hospital, Baltimore

Background: As an exceedingly rare benign mimicker of prostate cancer, the anatomic locations, histologic spectrum and immunohistochemical (IHC) profile of mesonephric remnant hyperplasia have not been well studied.
Design: We retrospectively studied 10 cases of mesonephric remnant hyperplasia involving the prostate and periprostatic tissue, including 8 cases at RP.
Results: Patients ranged in age from 48-70y (mean 60). 7 had concurrent prostatic adenocarcinoma and underwent RP; 1 underwent RP as a result of a misdiagnosis at an outside institution of mesonephric remnant hyperplasia as prostate cancer; and 2 had TURP for urinary obstruction. Lesions in the prostate and periprostatic tissue were concentrated in 2 areas: 1 was the anterior fibromuscular stroma and adjacent anterolateral periprostatic tissue (6/8); and the other was posteriorly and posterolaterally towards the base within the prostate or in periprostatic tissue, and around the seminal vesicle (4/8). Histological patterns included: small-medium acini/tubules with a lobular distribution (9/10), cysts with secretions either in clusters or scattered (8/10), small or ill-formed glands with an infiltrative growth (7/10), glands with papillary infolding or micropapillary tufts (4/10), and 2 cases exceptionally displayed nodules of ill-formed small glands intermixed with spindle cells, mimicking sclerosing adenosis or Gleason pattern 5 prostate cancer. Most cases (7/10) had ≥3 growth patterns. By IHC, all cases were negative for PSA. Cytokeratin 34βE12 was diffusely positive in 4/9 cases, and only focally in the remaining 5 cases. The intensity of 34βE12 was weaker than basal cells of adjacent prostatic glands. p63 was largely negative with only focal positivity in 4/7 cases. Racemase was focally positive in 4/7cases. Small glands with an infiltrative pattern, which most closely mimicked prostate cancer on H&E, often also had an IHC pattern typical of prostate cancer; glands were negative (3/6) or only focally positive (3/6) for 34βE12, negative for p63 (6/6), and focally positive for racemase (4/6). All cases were diffusely positive for PAX8.
Conclusions: This study by having RP material was able to show the novel finding of some cases of mesonephric remnant hyperplasia presenting as a florid growth anteriorly in the prostate, closely mimicking prostate cancer. Also a new H&E pattern was described. While basal cell markers and racemase are unreliable IHC markers, PAX8 and PSA are helpful to distinguish them from prostate adenocarcinoma.
Category: Genitourinary (including renal tumors)

Monday, February 28, 2011 1:00 PM

Poster Session II # 149, Monday Afternoon

 

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