Immunohistochemical expression of the mutant p53 protein and nuclear DNA content during the transition from benign to malignant breast disease

Abstract

Immunohistochemical expression of the cellular phosphoprotein p53 was investigated in archival, formalin-fixed, and paraffin-embedded surgical breast tissue specimens from 543 patients using the polyclonal antibody CM-1. Cytometric DNA assessments were performed on histopathologically or cytopathologically identified cell nuclei using image analysis. The series included five samples of normal resting breast parenchyma, 35 benign lesions including benign tumors, 54 hyperplastic lesions with and without atypia, 109 carcinomas in situ, and 340 invasive adenocarcinomas. In 56 of the latter cases specimens from corresponding lymph node metastases also were investigated. Mutant p53 protein expression was absent in normal resting parenchyma and in benign lesions, including benign tumors and epithelial hyperplasias. However, 14 of the 54 hyperplasias (26%) were found to be of DNA aneuploid type. Thirteen of 109 (12%) carcinomas in situ and 79 of 340 (23%) invasive neoplasms expressed the mutant p53 protein. Eight of nine (89%) p53 immunoreactive carcinomas in situ and 62 of 78 (80%) invasive carcinomas with p53 expression were DNA aneuploid. In invasive carcinomas p53 expression was absent in well differentiated neoplasms. In contrast, 58 of 158 (37%) poorly differentiated invasive carcinomas immunoreacted. Intraductal carcinomas of comedo type and poorly differentiated invasive carcinomas of comedo type expressed the mutant p53 protein in seven of 18 cases (39%) and in 14 of 22 cases (64%), respectively. The staining behavior of lymph node metastases was the same as that of the corresponding primary tumors. The present findings suggest that chromosomal alterations as indicated by DNA aneuploidy occur in precancerous lesions. However, immunohistochemically detectable accumulation of mutant p53 protein cannot be observed before the carcinoma in situ phase. The highest levels of p53 protein overexpression are found in invasive carcinomas and are closely associated with aneuploidy and poor differentiation. However, p53 overexpression apparently does not increase further during the tumor spread to lymph nodes.