Metastatic pancreatic carcinoma presenting as colon carcinoma.

Determining the origin of poorly differentiated adenocarcinomas remains a challenge for the pathologist. This manuscript reports the use of a panel of specific immunohistochemical stains to determine the primary site of a tumor in the colon. A 45-year-old man had a right hemicolectomy for adenocarcinoma. Immunohistochemical staining documented that the lesion was a metastasis from a primary pancreatic adenocarcinoma--an unusual pattern of spread. The case emphasizes the important use of immunohistochemistry in identifying the primary source of lesions, allowing for appropriate treatment and staging.