When adenocarcinomas arise within the esophagus, particularly when located away from the gastroesophageal junction, it may be important in some patients to differentiate between a primary esophageal adenocarcinoma and metastasis from another site. Lung adenocarcinoma is one tumor that has been reported to frequently metastasize to the esophagus.
To create a panel of immunohistochemical markers that can reliably distinguish between an esophageal and pulmonary primary; within the gastrointestinal pathology literature, including published articles and textbooks, common lung immunohistochemical markers, such as TTF-1, are assumed to be negative in esophageal adenocarcinoma, yet, to our knowledge, no study has yet investigated the veracity of that presumption.
In this study, 24 cases each of pulmonary and esophageal adenocarcinomas were stained with TTF-1, napsin A, CDX2, 34βE12, N-cadherin, and IMP3 in an attempt to define an optimal panel for differentiation. Esophageal adenocarcinomas occurring at the gastroesophageal junction were excluded in this study because a gastric primary tumor cannot be excluded in those cases.
Surprisingly, TTF-1 and napsin A were positive in similar proportions of tumors from both sites. Those markers that differentiated statistically between esophageal and pulmonary adenocarcinoma were IMP3, CDX2, and N-cadherin.
When differentiating the origin of a tumor as either esophageal or pulmonary, an immunohistochemical panel consisting of IMP3, CDX2, and N-cadherin is superior to either TTF-1 or napsin A.