[1017] Aberrant Staining Patterns for Prostatic Adenocarcinoma (PCA) in Needle Biopsies Using Triple Cocktail Immunohistochemistry (IHC): An Experience of 469 Cases with Rationale for the Selective Inclusion of Novel Cancer Specific Nuclear Marker MYC

DE Westfall, DJ Luthringer, AM Gown, RS Parakh, M Vankalakunti, MB Amin. Cedars-Sinai Medical Center, Los Angeles, CA; PhenoPath Laboratories, Seattle, WA

Background: The availability of racemase and basal cell-associated markers [high molecular weight cytokeratin (HMCK) and p63] in combination as a cocktail as a specific and sensitive panel for PCA has had great impact on the evaluation of needle biopsies, especially when dealing with atypical small acinar proliferations (ASAP) or unusual patterns of PCA. Recently, nuclear cellular anti-MYC antibody (C-MYC) expression has been reported as an early oncogenic event in prostate cancer.
Design: We reviewed 469 prostate biopsies from our routine practice and consult service that were stained with triple cocktail IHC to ascertain aberrant staining patterns in small acinar PCA. C-MYC IHC was performed in a subset of cases to evaluate its potential utility in cases with discordant patterns of staining.
Results: 233 cases were diagnosed as PCA, 147 were ASAP and 89 cases were determined to be benign based on IHC with close morphologic correlation. Nine of 233 (4%) PCAs were completely negative for racemase and 22 of 233 (9%) were weakly positive for racemase. Three (0.1%) typical cases of PCA were p63 positive, racemase positive and HMCK negative. Of cases diagnosed as ASAP, 48 of 147 (33%) cases were negative for racemase with positive or negative staining for basal cell-associated markers. C-MYC IHC performed on nineteen cases showed positive nuclear staining in 19 of 19 PCAs including 9 of 9 racemase positive, 4 of 4 racemase negative and 6 of 6 racemase weak cases. The percentage of cells staining positive for C-MYC ranged from 10% to 90% with moderate to intense staining. C-MYC was positive in the nuclei of cells of high grade prostatic intraepithelial neoplasia when present. There was some non-specific cytoplasmic staining of basal cells in occasional cases and rare positive staining in benign nuclei.
Conclusions: 1) Aberrant staining patterns may be seen in small acinar PCA, including racemase negativity and p63 positivity; the incidence of these discordant staining reactions is very low. 2) Awareness of non-typical IHC profiles by triple cocktail for PCA is important in the interpretation of small atypical foci. 3) Nuclear C-MYC positivity in PCA, including in racemase negative cases, shows the potential diagnostic utility of a fourth marker in select and diagnostically challenging cases.
Category: Genitourinary (including renal tumors)

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 144, Monday Morning


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