After a bilateral mastectomy, exome sequencing (Hiseq2500, Illumina, Cambridge, UK) of the right breast cancer and germline DNA revealed the germline PTEN mutation (c.T68G:p.L23X), and a second-hit somatic stop-gain PTEN mutation (exon 1, c.T264A:p.Y88X) with an allele frequency (AF) of 25.5%, alongside other variants (Fig 2A; Data Supplement). Here, PTEN is linked to breast cancer.