ESR1 and lung carcinoma: Breast cancer is the most common cancer diagnosed in 2022, according to the American Cancer Society, and it remains the second‐leading cause of cancer‐related death after lung cancer.[1, 2] Triple‐negative breast cancer (TNBC) refers to nearly 20% of breast cancers with negative expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), all of which are molecular targets of therapeutic agents.[3] Chemotherapy is the primary established systemic treatment for patients with TNBC in both early and advanced stages of the disease.