OBJECTIVES:To investigate the function of immunomarkers CK7, CK20, CK17, CDX2, MUC1, and MUC2 in the identification of primary ampullary carcinoma mixed subtype. METHODS:Forty-two cases of primary ampullary carcinoma were performed by immunohistochemical studies. The correlation between the mixed subtype and the other two subtypes and patient survival data was analyzed using the SPSS 16.0 statistical software. RESULTS:Among 42 cases, 12 (28.6%) cases were classified as mixed subtype, which showed variable expression patterns: 91.7% (11/12) for CK7, 83.3% (10/12) for CK20; 66.7% (8/12) for CK17, CDX2, and MUC1; and 50% (6/12) for MUC2. Ten (83.3%) mixed types coexpressed four or more immunomarkers. Eight (19%) intestinal subtypes mainly showed a positive expression of CK20, CDX2, and MUC2. Twenty-two (52.4%) pancreaticobiliary subtypes showed a positive expression of CK7, MUC1, and CK17. Stages III and IV diseases in mixed subtype (25%) and intestinal subtype (25%) were less than pancreaticobiliary subtype(63.6%) (p = 0.039). Follow-up data appeared to show a better survival rate for patients with mixed subtype than those with pancreaticobiliary subtypes. CONCLUSION:Immunohistochemical staining provided a more reliable means of diagnosing mixed ampulla carcinoma. Accurate subtyping of ampullary carcinoma is clinically important to select effective chemotherapy regimens and to assess disease prognosis.