[877] Utility of KI-67 and Triple Stain Cocktail in Facilitating the Diagnosis of Intraductal Carcinoma of the Prostate

Elizabeth Gersbach, Bing Zhu, Ximing Yang. Northwestern University, Chicago, IL

Background: Intraductal carcinoma of the prostate (IDC-P) is an uncommon entity that often accompanies high-grade, high-volume invasive prostatic adenocarcinoma. The morphologic description of IDC-P includes solid or loose architectural patterns, large and pleomorphic nuclei, and mitoses within the lumen of a duct that maintains the presence of basal cells. Diagnosis of IDC-P is based on histology, but distinguishing IDC-P from high-grade PIN (HGPIN) on core needle biopsy can be a challenge based on the H&E morphology alone. There is limited data on use of immunohistochemical stains in the diagnosis of IDC-P. The objective of this study is to determine if immunohistochemistry can be useful in the diagnosis of IDC-P.
Design: 18 cases of IDC-P were evaluated histologically. The cases included both prostatectomy specimens and prostatic core needle biopsies. Sections were stained with a triple stain cocktail (AMACR, p63 and HMWCK) and Ki-67. Areas of HGPIN, IDC-P, Gleason 3 (G3) and Gleason 4 (G4) patterns of adenocarcinoma were identified on H&E. IDC-P was identified based on H&E morphologic criteria as previously published and the presence of basal cells confirmed with basal cell staining. For the tissue stained with Ki-67, a minimum of 200 cells were counted. The percentage of cells with moderate-strong to strong Ki-67 staining was calculated for each of the four categories. T-tests were used for statistical analysis.
Results: IDC-P showed strong AMACR staining in 15 of 18 (83.3%) cases, while all of the HGPIN cases showed weak to moderate AMACR staining. All G3 and G4 areas showed strong AMACR staining (100%). The Ki-67 proliferative index (11.1±3.7%) of IDC-P was significantly different (p=<0.001) from that of HGPIN (1.5±0.7%). The Ki-67 proliferative rate for IDC-P was also different from but closer to Gleason pattern 4 (14.8±6.1%, p=0.012) and Gleason pattern 3 (9.2±2.6%, p=0.036) tumors.

Statistical Values For Prostatic Lesions
 HGPINIDC-PGleason 3Gleason 4
MEAN %1.511.19.214.8
STD %±0.7±3.7±2.6±6.1
P VALUEீ0.001N/A0.0360.012

Conclusions: The Ki-67 proliferative index for IDC-P was significantly higher than that of HGPIN, but intermediate between Gleason pattern 3 and Gleason pattern 4 areas of invasive prostatic adenocarcinoma. Strong AMACR staining, increased Ki-67 index, and the presence of basal cells are useful features for distinguishing IDC-P from HGPIN. The case number of this study is small and additional studies with larger number of cases are needed to substantiate the findings.
Category: Genitourinary (including renal tumors)

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 120, Wednesday Morning


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