This study is being done in order to better understand the biology of an abnormal lesion found in breast tissue called "lobular carcinoma in situ" (LCIS). We are interested in studying LCIS. The LCIS is not a cancer itself, but is a marker for an increased risk of cancer. We would like to look for LCIS in breast tissue removed during surgery from patients with cancer or at high risk for cancer. If LCIS is found, we will search for genes that are expressed (turned on or off) differently than in normal breast tissue. The identification of such genes would help us better understand the biology of LCIS, and its possible relationship to breast cancer.

LCIS) is a monoclonal pathologic entity which is subject to characterization at the molecular genetic level, and that these molecular genetic alterations may be used to predict the subsequent development of invasive breast cancer. Prophylactic mastectomy specimens from women with multifocal LCIS, and invasive breast cancer specimens which display coexisting LCIS, will be examined for X-chromosome inactivation patterns and loss of heterozygosity to assess for monoclonality. If clonality is present, we will assess for microsatellite instability, and a microarray-based comparative genomic hybridization (CGH) technique will be used to identify genetic alterations present in LCIS. Lastly, LCIS biopsy specimens from untreated patients who, after follow-up did or did not develop invasive breast cancer, will be evaluated to determine whether the nature or extent of any identified genetic alterations can be correlated with the subsequent development of invasive breast cancer. We hypothesize that a fraction of LCIS lesions will reflect a monoclonal origin, that those lesions of monoclonal origin will display evidence of specific molecular genetic alterations, and that these specific alterations will correlate with the likelihood of the subsequent development of invasive breast carcinoma.

Inclusion Criteria:

• multifocal lobular carcinoma in situ treated with prophylactic mastectomy or lumpectomy
• invasive breast cancer (lobular or ductal) with coexisting lobular carcinoma in situ treated with mastectomy or lumpectomy
• biopsy proven, untreated lobular carcinoma in situ
• invasive lobular cancer with or without coexisting lobular carcinoma in situ treated with mastectomy or lumpectomy

Exclusion Criteria:

• no paraffin blocks available
• no residual lobular carcinoma in situ in paraffin blocks

Women seen at MSKCC breast clinic