Interstitial deletion of the short arm of chromosome 3 as a primary chromosome abnormality in carcinomas of the breast.

Interstitial deletions of the short arm of chromosome 3 were found in short-term cultures of five breast carcinomas (of 41 breast cancers with clonal aberrations analyzed by us during the same period). They were the only clonal structural change in three tumors; in the remaining two, the clone with 3p-coexisted with seemingly unrelated clones that had other structural and numerical aberrations. The deletions were identical, del(3)(p12p14), in four cases. The fifth tumor seemed to have a smaller deletion, interpreted as del(3)(p13p14). Our findings constitute karyotypic evidence that 3p deletions are relatively common in breast carcinomas and concur with the molecular genetic detection of loss of heterozygosity in this chromosome arm. The fact that the deletions were found as solitary changes indicates that loss of genetic information from 3p loci is an early, possibly primary, event in tumorigenesis.