We anticipate that this IHC stain should be useful in a number of contexts, including: i) studies using tissue archives to explore the role of NOTCH1 in various neoplastic and non-neoplastic disorders; ii) selection of patients for trials of gamma-secretase inhibitors (GSIs) [21], the lead Notch pathway antagonists being tested in cancer patients, particularly trials involving diseases such as triple-negative breast cancer in which NOTCH1 activation is confined to a small subset of tumors; and iii) judging the efficacy of NOTCH1 antagonists in experimental models and in patients. Here, NOTCH1 is linked to triple-negative breast carcinoma.