Claudin-4 expression in Appendiceal Carcinoid

Background: Gastrointestinal carcinoids are frequently seen in the rectum and appendix. In the appendix, the size of the tumor and the involvement of the mesoappendix are important criteria for pathological staging. The bland looking of tumor cells gives an invaluable importance to the use of immunohistochemistry for size measurement and depth of invasion. The neuroendocrine markers such as synaptophysin and chromogranin commonly used to identify the neuroendocrine cells are also expressed by ganglion cells in the appendiceal wall. The cytokeratins such as AE1/3 used to confirm the epithelial nature of carcinoids are also expressed by mesothelial cells of serosa. WT-1 and Calretinin are mesothelial cell markers. In addition, calretinin can also be expressed by Schwann and neural cells. Claudins are components of tight junctions of epithelial cells and have been used to differentiate carcinomas from malignant mesotheliomas. In the current study we investigated the application of Claudin-4 as a specific marker in appendiceal carcinoids. Study Design: An incidental appendiceal carcinoid was found in a case of acute appendicitis from a 62-year-old woman. A panel of Immunohistochemistry including AE1/3, synaptophysin, Ki67, calretinin and claudin-4 was used to study the size and extent of the tumor.Results: Carcinois cells were correctly identified with expression of AE1/3 and synaptophysin in the muscularis propria of the appendix. The membranous expression of claudin-4 was diffusely but weakly seen in carcinoid cells; however, no staining was detected in the neuroal or mesothelial cells. This confirmed that the carcinoid in this case did not involve the mesoappendix.Conclusion: Claudin-4 can be used as a marker for carcinoid cells in appendix. Although this result is in contrary to lung carcinoids (Lung Cancer. 2007 Aug;57(2):159-67.), it confirms the recent observation that claudin-4 is expressed in rectal carcinoids (Oncol Rep. 2009 Jan;21(1):113-7.)

Claudin-4 expression in Appendiceal Carcinoid Keywords:

Claudin-4 , Carcinoid