Migrant non-screened women had higher proportions of unfavorable tumor characteristics than non-screened autochthonous women of the same age-group, i.e., positive lymph nodes (39.7% vs. 20.5%, p = 0.003), grade 3 (60.0% vs. 35.9%, p = 0.003), ER-negative (38.0% vs 18.8%, p = 0.003) and PR-negative (48.0% vs 31.5%, p = 0.027). The gene discussed is ESR1; the disease is neoplasm.