EGFR, KRAS, BRAF-mutations and microsatellite instability are absent in goblet cell carcinoids of the appendix

Goblet cell carcinoid (GCC) is a rare type of mixed endocrine-exocrine tumor of the appendix often showing a clinically aggressive behavior. On a molecular basis, this tumor is only poorly understood. To analyze possible molecular similarities between GCC and colorectal cancer, we examined 14 cases of GCC for mutations in exons 18, 19 and 21 of the EGFR-gene, exon 2 in the KRAS gene and for V600E mutations of the BRAF gene. Although the sensitive pyrosequencing method was used, no EGFR, KRAS or BRAF mutations could be found. Furthermore, using immunohistochemistry, no evidence for microsatellite instabillity (MSI) could be found. Despite the partial intestinal differentiation of GCC, our study indicates that the molecular pathogenesis of GCC significantly differs from conventional colorectal adenocarcinoma. This finding might also have implications in adjuvant chemotherapeutic treatment of advanced GCC.