I am not sure if there can be a complete list or database of Breast cancer genes anywhere, but this article from 2012 contains genes containing driver mutations: https://www.nature.com/articles/nature11017

Then there is of course the COSMIC database. https://cancer.sanger.ac.uk/cosmic Now if you search there for 'breast cancer' with a query like this: https://cancer.sanger.ac.uk/cosmic/browse/tissue?hn=carcinoma&in=t&sh=NS&sn=breast&ss=NS

A better gene set might be retrieved by going to the COSMIC gene census: https://cancer.sanger.ac.uk/cosmic/census?tier=all

and filtering the gene list for 'breast' (723 hits)

You receive over 24000 genes with mutations in one or the other sample. Most of them I propose are passenger mutations, see also: Driver And Passenger Mutations In Cancer

I believe that for a small number of known genes that is constantly expanded and changed, you will be better served by doing a comprehensive literature search through PubMed etc first. The task is to stay aligned with the current state of research and of course find more recent publications than the one I gave first:

• https://doi.org/10.1016/j.cell.2018.02.060
• https://www.nature.com/articles/s41568-018-0060-1

You can also check here :

Tumor portal : http://www.tumorportal.org/tumor_types?ttype=BRCA

ICGC portal : https://dcc.icgc.org/projects?filters=%7B%22project%22:%7B%22primarySite%22:%7B%22is%22:%5B%22Breast%22%5D%7D%7D%7D

GDC portal (TCGA) : https://portal.gdc.cancer.gov/exploration?filters=%7B%22op%22%3A%22and%22%2C%22content%22%3A%5B%7B%22op%22%3A%22in%22%2C%22content%22%3A%7B%22field%22%3A%22cases.primary_site%22%2C%22value%22%3A%5B%22Breast%22%5D%7D%7D%5D%7D&searchTableTab=genes