[879] Adenocarcinoma of the Prostate with Aberrant Expression of p63 (p63-PCa): A Radical Prostatectomy (RP) Study

Giovanna A Giannico, Hillary M Ross, Tamara L Lotan, Jonathan I Epstein. Vanderbilt Medical Center, Nashville, TN; Johns Hopkins Hospital, Baltimore, MD

Background: p63-PCa is an unusual subset of prostate cancer (PCa) with lack of ERG gene rearrangement and negative staining for high molecular weight cytkeratin.
Design: We reviewed the corresponding RP specimens of 27 needle biopsy cases of p63-PCa.
Results: Its frequency was 17 cases/year (0.3% of PCa) in one of the authors' consult service. Patients' mean age was 59 years. Of the 27 cases reviewed: 2 were excluded due to absence of residual PCa on RP; 1 due to hormone therapy affect; 2 with no identifiable p63-PCa (only residual usual-type PCa); and 1 with intense p63 cytoplasmic and nuclear staining. p63-PCa had in all cases a distinctive morphology consisting of atrophic glands, some poorly formed or solid, with multilayered often spindled nuclei. p63-PCa was 3+3=6 in 6 cases (28.5%), 3+5=8 in 8 cases (38%), 3+4=7 in 3 cases (14.3%), 4+3=7 or 5+3=8 in 2 cases (9.5%), and 5+4=9 in 2 cases (9.5%). Usual-type PCa coexisted in 18 cases (85.7%) with only p63-PCa present in the remaining 3 cases. The usual-type PCa was Gleason grade 3+3=6 in 13 cases (62%), 3+4=7 in 4 cases (19%), and 4+3=7 in 1 case 4%). Overall, p63-PCa represented 65% of the total cancer volume (median 80%). In 14 of 18 cases where usual-type and p63-PCa coexisted, the latter was present in separate nodules, whereas in the 4 remaining cases it was admixed with usual-type PCa. p63-PCa was present in the peripheral zone (PZ) in 16 cases (76.2%), extended from PZ to the transition zone in one case, and was adjacent to high grade PIN in 10 cases (47.6%). Tumor was organ-confined in 16 cases (76.2). In the remaining 5, 2 had p63-PCa extending to margin in areas of intraprostatic incisions, 2 had usual-type PCa extending to margin and extraprostatic tissue, respectively, and 1 had p63-PCa with an unusual cribriform morphology involving bladder neck. Ki-67 was low, <5% in all cases of p63-PCa, with similar expression in the coexisting usual-type PCa.
Conclusions: That almost all p63-Pca were confined to the prostate with low ki67 despite many cases with high Gleason score, argues that conventional Gleason grading system may not apply to these tumors. It is recommended that these tumors not be assigned a Gleason score and their relatively good outcome be noted. It is critical to recognize these unique cancers so that they may be graded accurately. In addition, it is important to recognize when p63/HMWCK basal cell cocktails are used when only nuclear p63 staining is present indicating a p63 positive cancer as opposed to a benign glandular proliferation.
Category: Genitourinary (including renal tumors)

Tuesday, March 5, 2013 11:45 AM

Proffered Papers: Section A, Tuesday Morning


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