Evaluation of biomarkers in breast and prostate cancer

p53, p185erbB-2, and epidermal growth factor (EGF) receptor are well-characterized biomarkers in invasive adenocarcinoma of the breast and in ductal carcinoma in situ. erbB-2 Protein (p185erbB-2) must be identified clearly on cytoplasmic membranes while cytoplasmic expression is ignored for breast cancers to be classified as overexpressing p185erbB-2. For p53, nuclear staining and the percent positive cells are considered, but rules for "cut-offs" are not defined. Evaluation criteria for biomarkers in prostate cancer are preliminary and the "rules" may not be the same as for breast cancer. Because the initial methods of fixation and tissue processing can change both the pattern and intensity of immunohistochemical identification of specific antigens and localization of receptors may change after the receptor-ligand interactions, we evaluated the effects of fixation both on the immunolocalization and intensity of expression of p53, p185erbB-2, and EGF receptor. We also studied the patterns of p185erbB-2 and p53 expression in a series of breast cancers evaluated concomitantly with a group of prostate cancers. Our results confirm that p53 mutations are common in breast cancer and that there is strong expression of p185erbB-2 on the membranes of a subset of breast cancers. The patterns of staining for both p53 and p185erbB-2 are different in prostate and breast cancers. A much lower proportion of prostate tumors than breast tumors have more than 10% of tumor cells with detectable nuclear p53 protein, but this proportion increases markedly in metastatic tumors or in primary stage D prostate cancer.(ABSTRACT TRUNCATED AT 250 WORDS)