ESR1 and invasive lobular breast carcinoma: During surveillance, a chest CT scan revealed a prominent axillary node, leading to a mammogram that identified a 7 mm invasive lobular carcinoma (ILC) of the right breast, grade 2, Estrogen Receptor/Progesterone Receptor (ER/PR) positive, Human Epidermal Growth Factor Receptor 2 (HER2) negative, with Kiel 67 (Ki-67) of 20% (cT1bN0M0).