Invasive lobular carcinoma (ILC) of the breast is known for its common presentation at an older age, and the frequent expression of favourable profile of estrogen and progesterone receptors (ER & PR) positivity, and human epidermal growth factor receptor 2 (HER2) negativity combined with low proliferation rate as measured by Ki67. This evidence concerns the gene PGR and invasive lobular breast carcinoma.