[223] Immunohistochemical Correlation of p53 with Unamplified Chromosome 17 Polysomy in Invasive Breast Carcinoma

U Krishnamurti, A Zarineh, F Atem, S Jan. Western Pennsylvania Hospital, Pittsburgh, PA; Allegheny General Hospital, Pittsburgh, PA; University of Pittsburgh, Pittsburgh, PA

Background: We have peviously demonstrated that unamplified chromosome 17 polysomy in invasive breast carcinoma (IBC) is associated with several increased adverse prognostic indicators in contrast to patients with neither amplification or polysomy (Mod Pathol 21(Supp 1):177: 41A, 2008). p53 IHC has been found to correlate with polysomy 17 in bladder carcinoma and head and neck squamous cell carcinomas. While p53 expression has been demonstrated to correlate with some adverse prognostic factors in IBC, its expression has not been correlated with HER2 amplification status or with polysomy 17. Herein, we examined p53 expression by IHC in cases of IBC showing unamplified polysomy 17 and compared it to cases with HER2 amplification and those with neither amplification or polysomy.
Design: A total of 135 cases of IBC, divided in three groups: N (neither polysomy or amplification, 44 cases), P (polysomy 17 without HER2 amplification, 53 cases) and A (HER2 amplification without polysomy 17, 38 cases) were compared for p53 immunostaining. The percentage of positively stained cells and the intensity of staining on a 1 to 3 scale were noted. p53 results were also correlated with HER2 and CEP17 copy numbers.
Results: 30/135 (22.2%) cases were positive for p53. All positive cases had > 25% cells with 2-3+ score with 74% cases having > 75% cells with 3+ score. 1+ staining in <10% cells was considered negative. 6.8% (3/44) of N, 24.5% (13/53) of P and 36.8% (14/38) of the A group were p53 positive. There was a statistically significant difference between the N group and both the P and A groups (p= 0.018 and 0.0008 respectively; 2 proportion Z test). The difference between the P and A groups was not statistically significant (p= 0.20). The mean CEP17 copy numbers for p53 negative and p53 positive cases was significantly different [2.6 (95% C.I 2.4-2.7) and 3.1(95% C.I 2.7-3.4), p= 0.007]. The mean HER2 copy numbers for p53 negative and p53 positive cases was also significantly different [5.2 (95% C.I 4.3-6.1) and 10.8 (95% C.I. 7.4- 14.1), p=0.000].
Conclusions: There is increased expression of p53 in unamplified polysomy 17 similar to that seen in HER2 amplification. P53 positivity correlates with CEP17 and HER-2 copy numbers. Therefore, p53 positivity, is additional support for the adverse prognostic significance of unamplified polysomy 17.
Category: Breast

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 52, Tuesday Morning