Molecular profile of atypical hyperplasia of the breast.

PURPOSE: Atypical ductal and atypical lobular hyperplasia (AH) of the breast are important proliferative lesions which are associated with a significantly increased risk for breast cancer. The breast cancer which develops in association with AH may occur synchronously, representing local progression, or metachronously at a later date in either the ipsilateral or contralateral breast. These high-risk characteristics of AH suggest they contain significant genomic changes.

METHODS: To define the genomic changes in AH, a comprehensive review of the literature was conducted to identify the numerical chromosomal and structural chromosomal changes, DNA methylation, and gene expression abnormalities in atypical ductal and atypical lobular hyperplasia.

RESULTS: AHs are characterized by advanced genomic changes including aneuploidy, loss of heterozygosity, gross chromosomal rearrangements such as amplifications and large-scale deletions, DNA methylation of tumor suppressor and other genes, and gene expression differences between AH and surrounding normal breast tissue including significant estrogen receptor expression. Many of these changes are shared by an associated synchronous breast cancer, consistent with an important precursor role for AH. At the same time, many of the genomic changes of AHs are also shared by common sporadic breast cancer, consistent with a high risk for future development of metachronous breast cancer.

CONCLUSIONS: This molecular profile should help clarify the genomic characteristics and malignant predisposition of AH, and aid in the identification of new targets for the prevention of breast cancer.