Pan‐cancer expression analysis of TCGA‐BRCA (n = 1,085) and CPTAC (n = 122) datasets identified ARL3 as the only gene consistently overexpressed in tumor versus matched normal tissues after excluding other genes without significant prognostic associations, with pronounced enrichment in luminal A/B subtypes (Figure 1B–D; Figure S1A–F, Supporting Information). The gene discussed is ARL3; the disease is cancer.