ABSTRACT
It i s evident in other contributions to this volume that cytogenetic analysis has been critical to the localization, identification, and cloning of genes that define tumor development in many differentiated tissues . In contrast, breast cancer-specific cytogenetic associations have been elusive, hampered by the inherent heterogeneity, slow growth, and other features characteristic of breast cancer biology. Although almost 400 breast carcinomas were included in the last Catalog of Chromosome Aberrations in Cancer ( 1 ) , many still were derived from effusion fluids and solid metastatic lesions, and many were incompletely karyotyped, reflecting the difficulties in analysis of pri mary breast carcinomas . The most prevalent aberrations reported have been gains of chromosomes 7, 8, 1 8 , and 20; loss of chromosome 1 7 ; and struc tural rearrangements of 1q, 3p, and 6q. However, many other alterations, singly and combined, have been reported, and there is little agreement on identification of the earliest relevant events. At least some of the heteroge neity of karyotypic findings in breast cancer may be attributable to differing pathways of breast carcinogenesis . Until recently, little attention has been paid by cytogeneticists to the differences in disease stage and pathologic classification that may contribute to the marked variations observed in ex isting cytogenetic data. The existing complex and often confusing accumu lated data have been reviewed recently (2-4). This chapter will focus largely on new findings and alternative cytogenetic approaches .
