Ampulla of Vater carcinoma: Molecular landscape and clinical implications

Table 1 Proposed immunohistochemical markers for ampulla of Vater carcinoma histological classification (adapted from Mafficini et al[16])

Immunohistochemical marker criteria present	Intestinal type	Pancreatobiliary type positive	Mixed/Ambiguous type	Note
Ang et al[12] (MUC1, MUC2, CDX2, CK20)	Positive CK20 or CDX2 or MUC2, and negative MUC1 Positive CK20 and CDX2, and MUC2 and any MUC1	Positive MUC1 and negative CDX2, and negative MUC2 and any CK20	All other combinations
Chang et al[13] (MUC1, CDX2)	Positive CDX2 or negative MUC1	Negative CDX2 and positive MUC1	Not applicable	CDX2 positivity based on H score (percentage of positive cells × intensity of staining) > 35 MUC1 positivity based on any staining
Gingras et al[17] (MUC1, CDX2)	Ratio of the CDX2/MUC1 H score ≥ 2	Ratio of the CDX2/MUC1 H score < 0.5	Ratio of CDX2/MUC1 H score ≥ 0.5 and < 2	Use only MUC1 and CDX2 as per Chang et al[13], with H scores for both CDX2 and MUC1
Mafficini et al[16] (MUC1, MUC2, CDX2, CK20)	Positive CK20 or CDX2 or MUC2, and negative MUC1	Positive MUC1 and negative CDX2, and negative MUC2 and any CK20	All other combinations