Her diagnostic assessment included (1) a left breast ultrasound which showed a macro-lobulated mass with Doppler positive blood flow and internal echoes measuring 3.4 × 2.3 × 2.6 cm, (2) core needle biopsy of the lesion showed a grade 3 invasive ductal carcinoma (Fig. 1a) that was estrogen receptor (ER) (Fig. 1b) and progesterone receptor (PR) positive (100% and 10% positivity, respectively) and HER2 negative by  fluorescence in situ hybridization (HER2/CEN17 ratio = 1.0). The gene discussed is ESR1; the disease is invasive ductal breast carcinoma.