Molecular clonality relationships in initial carcinomas, ipsilateral breast failures, and distant metastases in patients treated with breast-conserving therapy: evidence suggesting that some distant metastases are derived from ipsilateral breast failures and that metastases can metastasize.

We studied the clonality relationships in invasive breast carcinomas, ipsilateral breast failures (IBFs), and distant metastases (DMs) using a polymerase chain reaction-loss of heterozygosity (LOH) clonality assay to determine whether IBFs can be the source of DMs. Six cases of initial carcinomas, IBFs, and DMs were identified. Carcinoma DNA was extracted from paraffin blocks and analyzed with 20 markers. In 2 cases, the LOH pattern suggested the DM directly resulted from the IBF. In 2 cases, the initial carcinoma, IBF, and DM were one progressive, genetically unstable process. Separate subclones in the initial carcinoma gave rise to the IBF and DM in 1 case, and the DM derived from a second IBF in 1 case. The relationships of initial carcinomas, IBFs, and DMs are complex. DMs seem to be the direct result of IBFs in some cases. Some carcinomas seem to be composed of subclones with different and unrelated IBF and DM potential.