Cancer cytogenetics is the investigation of acquired chromosome changes in tumor cells of an individual with a normal constitutional chromosome complement. Although the first tumor specific chromosome change, the Philadelphia chromosome associated with CML, was identified in 1961, most of the information in this field derives from the past ten years. Recent advances in primary cell culture techniques now allow the study of karyotype, abnormalities in solid tumors, thus permitted the analysis of the role of chromosomal disruption in tumorgenesis. The cytogenetics core will perform karyotype studies on lymphomas and cell lines derived from lymphoma heterographs to ensure the phenotypic fidelity of tumor cells after in vivo and in vitro manipulations for projects 1, 2 and 3. This core will also perform cytogenetic analysis of thyroid and ovarian neoplasms (projects 4 and 6), which will help localize potential sites for tumor suppressor genes which may be lost or inactivated in these common endocrine tumors.