[293] p27 and Ki-67 in Invasive Breast Carcinoma with Unamplified Chromosome 17 Polysomy.

Oleksandr Yergiyev, Jan F Silverman, Uma Krishnamurti. Allegheny General Hospital, Pittsburgh, PA; Western Pennsylvania Hospital, Pittsburgh

Background: p27 is a cyclin dependent kinase inhibitor and Ki-67 is a cell proliferation marker. While decreased p27 and increased Ki-67 expression have been demonstrated to be adverse prognostic factors in invasive breast carcinoma(IBC), their expression has not been correlated with HER2 amplification or with chromosome 17 polysomy. We have earlier demonstrated that IBC with unamplified 17 polysomy is associated with several adverse prognostic indicators, including increased p53 positivity, with p53 positive cases being similar to cases with HER2 amplification (Appl Immunohistochem Mol Morphol, e-pub Sept 2010). The aim of this study was to correlate p27 and Ki-67 staining with chromosome 17 status and p53 positivity.
Design: Polysomy 17 was defined by the presence of greater than three chromosome 17 centromere copies/cell. Three groups: N (no polysomy and no amplification, 30 cases), P (17 polysomy without Her2 amplification, 43 cases) and A (Her2 amplification without 17 polysomy, 27 cases)were stained for p27 and Ki-67. Percentage of Ki-67 positive cells was noted. The product of the percentage of positive cells and intensity of staining on a 0-3 scale was noted as p27 score. Staining results were correlated with amplification/polysomy and p53 status.
Results: The mean ±SEM p27 score in N, P and A was 136±20, 116±16 and 104±20 respectively. Although the results show a decreasing trend, the difference was not statistically significant. Mean p27 score did not show significant correlation with p53 status.
The mean Ki-67 index in groups N, P and A was 8, 12 and 13 respectively (not statistically significant). The table shows the distribution of Ki-67 index in the three groups. While both groups P and A show a greater percentage of cases with Ki-67 > 10%, the differences were not significant.

Ki-67 Index
 n1-10%11-25%26-50%>51%
N3025/30 (83%)2/30 (7%)2/30 (7%)1/30 (3%)
P4328/43 (65%)8/43 (19%)6/43 (14%)1/43 (2%)
A2715/27 (55%)8/27 (30%)4/27 (15%)0/27 (0%)


Within group P, p53+ cases (23%) had a higher mean Ki-67 index of 24 versus 9 in the p53- group (P=0.0027).
Conclusions: In IBC with unamplified chromosome 17 polysomy, Ki-67 index correlates with p53 positivity. Along with p53, Ki-67 may be of value in identifying a subset of unamplified chromosome 17 polysomy cases that are have more adverse prognostic factors and may benefit from more aggressive therapy. p27 failed to show significant correlation with polysomy 17, HER2 amplification, or p53 status.
Category: Breast

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 13, Tuesday Afternoon

 

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