Summary of validation of somatic variation in the IFNAR1 locus.

Summary of Illumina SNP genotyping, which suggested structural variation within the hypevariable region and results from subsequent confirmation using Sanger sequencing and agarose gel electrophoresis. One (*) and two (**) asterisks after the subject ID indicate patients with breast cancer and pairs of monozygotic twins, respectively. BL, UM and PT stand for DNA from peripheral blood cells, healthy morphologically normal breast tissue from a patient affected with breast cancer and primary breast tumor, respectively. “Seq” indicate that the somatic mosaicism was verified by Sanger sequencing while “Gel” shows that it was confirmed by estimation of allele sizes from agarose gel.