ESR1 and neoplasm: Tumor cells showed a negative reaction for estrogen receptor (ER), progesterone receptor(PR), gross cystic disease fluid protein-15 (GCDFP-15), mammaglobin, hepatocyte paraffin 1 (Hep Par1), thyroid transcription factor-1 (TTF-1), mucin 2 glycoprotein (MUC2) and cytokeratin 20 (CK20) (Figure 3); and a positive reaction for mucin 1 glycoprotein (MUC1), caudal type homeobox 2 (CDX2), E-cadherin (E-ca) and cytokeratin 7 (CK7), but weak expression focal for E-ca (Figure 4).