In terms of tumor characteristics, interval cases were diagnosed with more tumors with poorer prognosis than screen-detected cases; estrogen receptor (ER)-negative (ER-) (30 % vs 18 %, P < 0.01), progesterone receptor (PR)-negative (PR-) (54 % vs 43 %, P = 0.02), poorly differentiated tumors (41 % vs 27 %, P < 0.01), positive nodal status (44 % vs 16 %, P < 0.001), and larger tumor size, ≥2 cm (44 % vs 20 %, P < 0.001). The gene discussed is ESR1; the disease is neoplasm.