In addition to invasive tumour samples, 23 normal
samples were isolated from adjacent tissue. These
included whole breast lobules (epithelial cells of acini
and terminal ducts and myoepithelial cells) and epithelial
cells of larger ducts, wherever possible (Fig. 3c).
Nine separate ductal carcinoma in situ (DCIS) samples
of low, intermediate or high-grade, including exclusively
epithelial cells, were also isolated. In the case of high-
grade DCIS, necrosis was dissected and removed from
the section (Fig. 3d).
Sampling of normal and in situ tissues was focussed
on patients where the germline genotype was heterozygous
for one or both SNPs.