Chromosome 11 aneuploidy detected by fluorescent in situ hybridization (FISH) in breast cancer: relation with progesterone receptor expression.

Progesterone receptor (PR) expression is known to be impaired in breast cancer. As the PR gene is located on chromosome 11 which is also often affected, we studied their relationship in 15 patients with breast carcinoma. Tumoural imprints were used for PR immunocytochemistry and for FISH with chromosome 11 centromeric probes. Distribution profiles of chromosome 11 number in PR+ and PR- cell populations were examined. No difference in the number of chromosome 11 was found between PR+ and PR- breast tumours. Thus, loss of PR expression in breast cancer cannot be explained only by loss of chromosome 11; other genetic or non-genetic mechanisms should be advanced.