A 59-year-old woman with a history of estrogen/progesterone receptor positive (ER/PR+) and human epidermal growth factor receptor 2 negative (HER2−) invasive lobular carcinoma (ILC) of the breast, previously treated with tamoxifen, presented with 2 weeks of immediate postprandial vomiting and generalized weakness. This evidence concerns the gene PGR and invasive lobular breast carcinoma.