Fig. 5.18 Goblet cell carcinoid tumour. A Typical concentric mural distribution of tumour with preservation of the appendiceal lumen. Mucin positive tumour nests (green) are seen in this Movat stain. Lumen is compressed, but intact. B Typical clusters of goblet cells. C Chromogranin A positive cells.

and the argyrophil reaction in 89% of cases {2059}. Useful criteria for diagnosing this tumour are origin from the base of the crypts, integrity of the luminal mucosa, orderly arrangements, and absence of cytological abnormalities and mitoses. Immunohistochemically, tumour cells are often positive for chromogranin A, glucagon, serotonin, and IgA, while they are unreactive for S100 protein {586, 209}.

Mixed carcinoid-adenocarcinoma. This term has been proposed to designate carcinomas of the appendix that arise by progression from a pre-existing goblet-cell carcinoid. These carcinomas occur in the apparent absence of neoplastic change in the mucosal epithelium {209}.

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