[936] Immunohistochemical Expression of Prostate-Specific Antigen (PSA), Prostatic Acid Phosphatase (PAP) and Antibody Cocktail (P63/HMWCK/AMACR) in Ductal Adenocarcinoma of the Prostate.

Hemamali Samaratunga, Michael Adamson, John Yaxley, Brett Delahunt. Aquesta Pathology, Brisbane, QLD, Australia; University of Queensland, Brisbane, Australia; Royal Brisbane Hospital, Brisbane, QLD, Australia; University of Otago, Wellington, New Zealand

Background: Ductal adenocarcinoma of the prostate (DAP) is an aggressive variant of prostatic adenocarcinoma displaying several architectural patterns mimicking carcinoma from other organs. Prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) immunostaining is frequently used to establish prostatic origin. The extent of immunostaining for these in DAP has not been studied, particularly the significance of negative staining in a small biopsy. The extent of immunostaining for AMACR and basal cell markers relating to different architectural patterns in DAP has also not been fully examined.
Design: Immunohistochemical staining for monoclonal PSA (Clone ER-PR8, Dako, Denmark), monoclonal PAP (Clone PASE/4LJ, Dako, Denmark) and antibody cocktail 34betaE12, p504s (AMACR), and p63 was performed on paraffin sections containing DAP from 50 radical prostatectomy specimens. Staining was categorized as negative (0%), 1+ (1-30%), 2+ (31-60%) or 3+ (61-100%). The percentage of tumor negative for PSA and PAP in the same area was noted.
Results: Thirty nine cases had cribriform, 11 papillary, 7 solid and 35 glandular architecture (34 had >1pattern). PSA was positive in 92%; 1+ in 24%, 2+ in 20% and 3+ in 48%. PAP was positive in 94%; 1+ in 6%, 2+ in 28% and 3+ in 60%.Both PSA and PAP were negative in the same area in ≥30% of tumour in 28%, including 1 entirely negative for both. These represented 30% of cribriform, 36% papillary, 15% solid and 22% glandular patterns. AMACR was positive in 84% but negative in ≥30% of tumour in 90%. Basal cells were undetected by 34betaE12 and p63 in 46% and patchy in 1-30% of tumour in 42%. These included 84% of cribriform, 100% of papillary and 85% of solid pattern. All glandular lesions were entirely devoid of basal cells.
Conclusions: Absence or minimal retention of basal cells in all patterns of DAP confirms that this is not intraductal carcinoma but a distinct variant of prostatic adenocarcinoma. Although only 2% were entirely negative for PSA and PAP, nearly one third had large areas negative for both irrespective of architectural pattern. AMACR was positive in the majority of DAP, however, large areas were negative. Negative staining for these markers in small volumes of tumor as seen in biopsies does not rule out a diagnosis of DAP.
Category: Genitourinary (including renal tumors)

Monday, February 28, 2011 1:00 PM

Poster Session II # 156, Monday Afternoon


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