Previous twin studies show that genetic factors are responsible for 63% of the variability
in breast density. We analyzed the mammographic images of 9 discordant twin pairs
for breast cancer from the population-based Hungarian Twin Registry. We measured breast
density using 3D Slicer software. Genetic variants predisposing to breast cancer were
also examined. One of the examined twin pairs had a BRCA2 mutation in both members.
There was no significant difference between the mean values of breast density in the
tumor and non-tumor groups (p=0.323). In terms of parity and the presence of menopause,
we found mostly no significant difference between the members of the twin pair. In
our cohort of identical twins discordant for breast cancer, the average breast density
showed no significant difference, which can be explained by the common genetic basis
of breast cancer and breast density.