[Signet ring cell carcinoid of the appendix. Morphological, histochemical and immunohistochemical study of a case].

A case of carcinoid tumor of the appendix with "signet ring" cells pattern and asymptomatic clinical course is presented. The tumor was detected during a Bilroth I gastrectomy procedure. Mucin-secreting cells with cytoplasms often containing argentaffin and argyrophil granules was the predominant histologic pattern. Lack of neuron-specific enolase activity and their positivity for lysozyme and EMA marker indicate an origin from crypt cell and not a neural crest source. After simple appendectomy, the patient was healthy 3 years following surgery.