Confirmation of the copy number of chromosome 1 in interphase nuclei from paraffin sections of breast tumours by fluorescence in situ hybridization.

Fluorescence in situ hybridization (FISH) was used to establish the copy number of chromosome 1 in a set of nine breast tumours in which the chromosome had previously been shown to have undergone a variety of rearrangements by loss of heterozygosity studies. In each case, FISH with satellite III DNA from chromosome 1q12 confirmed the results obtained by Southern hybridization. Importantly, in all five cases with rearrangements thought not to involve the centromeric region, FISH showed that the events had not disrupted the gross chromosome structure. This study highlights the potential of using the two techniques together to obtain a clearer picture of both large- and small-scale alterations to chromosomes in solid tumours.