Intestinal, intestinal-type and intestine-localized metastatic adenocarcinoma. Immunohistochemical approach to the differential diagnosis.

The pathologist is often called to define the origin of tumors through the help of ancillary studies, mainly immunohistochemical stainings. In this setting, the differential diagnosis between intestinal adenocarcinomas, other tumors with intestinal-type morphology, and adenocarcinomas metastatic to the bowel can be particularly difficult. In such cases, an accurate assessment of the disease is required to address the patients to the optimal treatment. Immunohistochemistry offers the use of multiple antibodies: the integrated evaluation of specific stainings can lead to a correct diagnosis. Particularly, the use of cytokeratins, mucins, and β-catenin could be of great help in most cases. In addition, recently, novel specific markers such as SATB2 and AMACR have been introduced, improving the utility of immunohistochemistry in the differential diagnosis of intestinal-type and intestinal adenocarcinomas.