A particular value, such as “greater than 25” in the 21-gene Recurrence Score assay, which indicates that patients with an estrogen receptor–positive breast cancer would benefit from chemotherapy, or a range of values, such as 1 to 25 in the same assay, indicating who can safely forego chemotherapy, would be more practicable in the clinical field [30,31]. Here, ESR1 is linked to breast carcinoma.