A 51-year-old female underwent right mastectomy and axillary dissection in 2008 for Stage 3 (T2N2M0) invasive lobular carcinoma of the right breast which was negative for estrogen (ER) and progesterone receptors (PR), and equivocal for human epidermal growth factor receptor 2 (HER2). This evidence concerns the gene PGR and invasive lobular breast carcinoma.