Cytogenetic studies of primary and metastatic breast cancer

A series of primary and metastatic breast carcinomas obtained from female and male patients were cytogenetically analysed. Trisomy 12 was identified as a recurrent and sometimes early event in breast carcinogenesis. Also, multiple polysomies involving chromosomes 1, 5, 6, 7, 12, 16, 18, and 19 were identified as a possible pathway of progression in a subset of carcinomas. Among the male breast carcinomas, +7, del(16)(q13) and +20 were identified as recurrent changes. A study of invasive breast carcinomas of histological types usually considered to be prognostically favourable revealed that medullary carcinomas are cytogenetically more complex than mucinous and tubular carcinomas, with medullary carcinomas often exhibiting karyotypic features that have previously been associated with aggressive breast carcinomas, i.e., highly complex chromosome aberrations with near-triploid chromosome numbers. A cytogenetic comparison of primary breast carcinomas and their lymph node metastases, as well as a comparison of chromosomal imbalances in node-positive and node-negative primary breast carcinomas, showed that monosomy for chromosomes 17, 18, and 22 seem to be important in the metastatic process. On the other hand, loss of material from the proximal part of the long arm of chromosome 6 and loss of the long arm of chromosome 16 were preferentially associated with a node-negative phenotype in primary breast cancer.