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 can cer. As the PR gene is located on chromosome 11 which is also often affecte d, we studied their relationship in 15 patients with breast carcinoma. Tumo ural imprints were used for PR immunocytochemistry and for FISH with chromo some II centromeric probes. Distribution profiles of chromosome 11 number i n PR+ and PR- cell populations were examined. No difference in the number o f chromosome II was found between PR+ and PR- breast tumours. Thus, loss of PR expression in breast cancer cannot be explained only by loss of chromos ome II, other genetic or non-genetic mechanisms should be advanced.