Correlation of immunohistochemical expression of p53 with unamplified chromosome 17 polysomy in invasive breast carcinoma.

p53 functions as a tumor suppressor gene and is frequently mutated and inactivated in several human cancers. Some studies have shown p53 overexpression in breast cancer to be an independent prognostic indicator. A subset of breast cancers have chromosome 17 polysomy. Although p53 immunostaining has been found to correlate with chromosome 17 polysomy in nonsmall cell lung carcinomas, head and neck squamous cell carcinomas, and bladder carcinomas, its expression has not been correlated with chromosome 17 polysomy in breast carcinomas. In this study, we compared p53 expression by immunohistochemistry in cases of invasive breast carcinoma showing unamplified chromosome 17 polysomy (P) with cases showing HER2 amplification (A) and with those showing neither amplification nor polysomy (N). There was a significant overexpression of p53 in both cases with HER2 amplification and unamplified polysomy 17 compared with cases with neither amplification nor polysomy (7% of N, 25% of P, and 37% of A group were p53 positive). We have shown in an earlier study that invasive breast carcinoma with unamplified chromosome 17 polysomy is associated with several adverse prognostic indicators including a higher Nottingham score and greater estrogen receptor (ER) negativity with a trend toward the amplified group, in contrast to patients with neither amplification nor polysomy. In this study, we now show that p53 positivity in unamplified 17 polysomy identifies cases that are associated with an even higher Nottingham score and greater hormone receptor negativity that is similar to cases with HER2 amplification.