Goblet cell carcinoid tumour of the appendix.

Goblet cell carcinoid tumors (GCCT) are uncommon neoplasms that predominantly occur in the vermiform appendix. They tend to occur in middle-aged adults with a near equal sex distribution. Most Goblet cell carcinoid tumors are discovered in appendices removed for acute appendicitis and for other reasons. Goblet cell carcinoid tumors demonstrate features of both classic carcinoid tumor and adenocarcinoma. Similar to classic carcinoid tumors, GCCT may involve the deep mucosa, but are not associated with dysplasia of the surface epithelium. The GCCT cells grow as nests, cords, and clusters in collagenous stroma. They contain abundant cytoplasmic mucin and display mild cytological atypia with a relatively low proliferation index, as measured by Ki-67 stain. Immunohistochemical stains for neuroendocrine markers, such as chromogranin and synaptophysin, demonstrate patchy positive staining of tumor cells.