Amplification of CCND1 and expression of its protein product, cyclin D1, in ductal carcinoma in situ of the breast.

Ductal carcinoma in situ (DCIS) of the breast is a heterogeneous disease clinically and biologically. The few available studies of its natural history implicate DCIS as a non-obligate precursor for invasive carcinoma. We have used fluorescence in situ hybridization (FISH) to detect gene amplification of the cell cycle regulator gene CCND1 in 88 examples of formalin-fixed, paraffin-embedded DCIS. Expression of its protein product cyclin D1 was detected by immunohistochemistry. CCND1 was amplified in 18% of DCIS cases. High grade DCIS was more likely to show amplification than low grade DCIS (32% versus 8%; P = 0.08). Gene amplification was associated with cyclin D1 protein expression (P = 0.001), although cyclin D1 was detected in cases that did not demonstrate gene amplification. Overall, cyclin D1 protein was detected in 50% of DCIS cases. Although only 2 of 23 (8%) cases of low grade DCIS had CCND1 amplification, over 50% (13/23) of these cases expressed cyclin D1 protein. Low grade DCIS had a higher mean percentage of nuclei expressing cyclin D1 than did intermediate or high grade DCIS (P = 0.007). Mechanisms other than gene amplification may be responsible for increased cyclin D1 protein in DCIS, especially in low grade DCIS. Identifying mechanisms that control cell cycle progression in DCIS may yield clues to its biological behavior.

Genetic heterogeneity of primary and metastatic breast carcinoma defined by fluorescence in situ hybridization.

Breast carcinoma is frequently associated with nonrandom chromosomal aberrations, but their identification by standard cytogenetics (SC) is often limited by technical difficulties. Fluorescence in situ hybridization (FISH) studies of interphase nuclei can circumvent some of these difficulties and has the potential to identify nonrandom molecular cytogenetic events occurring in breast cancer. FISH was performed on tumor nuclei isolated from 15 formalin-fixed, paraffin-embedded archival breast carcinomas using a panel of chromosome-specific alpha-satellite probes for enumerating chromosomes in interphase nuclei. Freshly isolated cells from these same cases had previously been studied by standard cytogenetics and FISH. In addition to archival primary carcinoma, archival metastases and normal tissue were also studied by FISH. Genetic numerical alterations were identified by standard cytogenetics or FISH in 14 of 15 carcinomas. Numeric alterations initially identified by standard cytogenetics were confirmed by FISH in 9 of 10 cases. Results of FISH performed on nuclei isolated from paraffin-embedded material were in agreement with FISH performed on freshly isolated cells. Clonal numeric alterations were observed in the archival primary tumor as well as in metastases. Archival normal tissue was consistently disomic.