Small intestinal adenocarcinomas (SACs) are rare malignancies of the alimentary tract with uncertain carcinogenesis.

We investigated the expression of deleted in pancreatic cancer 4 (DPC4) in 188 cases of surgically resected SACs, using tissue microarray technology.

Twenty-four of the 188 tumors showed complete loss of Smad4/DPC4 expression in cytoplasm (score, 0; 12.8%). Eighty-four and 31 cases were moderately and strongly positive, respectively (score, 2 and 3; 44.7% and 16.5%, respectively) and 49 cases were focally or weakly stained (score, 1; 29.1%). Immunohistochemistry analysis showed that the expression of Smad4/DPC4 was related to an increased risk of lymphatic invasion but not to other clinicopathological features of the tumors (tumor location, differentiation, growth pattern, T stage, direct invasion, vascular invasion, and nodal metastasis). There was no significant association between Smad4/DPC4 expression and patient survival.

The present research is the first study to evaluate Smad4/DPC4 expression in a large sample of SACs with clinicopathologic correlation. Future studies should focus on the immunohistochemical and molecular characteristics of SACs to clarify their tumorigenesis.