As atypia became more severe, the level of ATF6 expression increased; the median ATF6-IHC score was 2.0 (range, 0–4) in adenoma with moderate atypia, 5.0 (range, 0–8) in adenoma with severe atypia, and 7.0 (range, 3–14) in pTis cancer. Here, ATF6 is linked to cancer.