Adenocarcinoid of ileum and appendix, incidentally discovered during exploratory laparotomy for gastric MALT lymphoma, with subsequent diffuse prostatic metastases: report of a case with light, immunohistochemical, and electron microscopic studies.

The diagnosis of adenocarcinoid (mucinous/goblet cell carcinoid) is usually unexpected by both clinicians and pathologists. We report here the case of a 74-year-old man with gastric lymphoma (B-cell MALToma) diagnosed by endoscopy, who was found on exploratory laparotomy also to have extensive intraabdominal involvement by adenocarcinoid, arising from the ileum and/or appendix. The patient died two years after diagnosis with bladder outlet and small bowel obstruction due to diffuse metastases. In addition to mucin positivity, immunohistochemical stains demonstrated the tumor to be positive for chromogranin, synaptophysin, serotonin, gastrin, and glucagon. Of histogenetic interest, some individual neoplastic cells appeared to be positive for both mucin and chromogranin, and this was confirmed by the electron microscopic finding of microvilli, intracytoplasmic mucin droplets, and neurosecretory granules involving the same neoplastic cells. This also appears to be the first reported case of adenocarcinoid associated with lymphoma and demonstration of histochemical/immunohistochemical and ultrastructural evidence of cellular components with dual mucinous adenocarcinoma and neuroendocrine features, and the second reported case to have prostatic metastases.