The image shows well-defined clusters of goblet cells lacking significant cytologic atypia infiltrating the muscular wall of the appendix. There is no desmoplastic response. This would be classified as typical GCC, group A, according to the classification proposed by Tang et al (Am J Surg Pathol 2008; 32:1429-1443). GCC's show mixed phenotype, with neuroendocrine as well as goblet cell (glandular) differentiation. They are considered to be distinct from both classic carcinoids of the appendix as well as de novo appendiceal adenocarcinomas. A variety of descriptive terms have been used to refer to GCC, including adenocarcinoid, mixed carcinoid-adenocarcinoma, amphicrine carcinoma, and crypt cell carcinoma. It is best to avoid use of such terms.