In the Original Investigation titled “Artificial Intelligence Algorithms to Assess Hormonal Status From Tissue Microarrays in Patients With Breast Cancer,”1 published July 26, 2019, the labeling of the tan and navy lines in the key of Figure 3C were inadvertently switched. The navy line should indicate “1% ≤ ER < 25%,” and the tan line should indicate “75% ≤ ER ≤ 100%.” This article has been corrected.1