To clarify the mechanisms responsible for the silencing of PTEN expression, we carried out an analysis of primary breast cancer samples, adjacent normal epithelial tissue, and existing breast cancer datasets for genes that could be responsible for PTEN loss of expression and determined that NOTCH1 or NOTCH2 alterations (mutation, fusions, or overexpression) occur in a large proportion of TNBC cases exhibiting PTEN downregulation. The gene discussed is PTEN; the disease is breast carcinoma.