Patient  psychiatrique de  55  ans,   asthmatique,  PMD  depuis  30  ans  sous  traitement ( Anafranil, Tifranil, Seroxate ), chez qui on découvre une anémie ferriprive il y a deux ans sur un bilan pour pneumonie.

Gastroscopie : gastrite antrale rayon de roue. Lésions fundiques  polypoïdes érodés.

A noter que le patient est constipé depuis 30 ans, sans autres symptomatologie digestive, avec apparition depuis deux mois de flush au visage, survenant tous les 2-3 jours de 2-3h de durée. Une gastrectomie totale est réalisée aprés confirmation tumorale biopsique.

Grossly, gastric carcinoid tumors tend to be small, sharply outlined, and covered by a flattened mucosa. They may also have the appearance of gastric polyps.

Microscopically, the predominant pattern of growth may be microglandular, trabecular, orrarelyinsular. The nuclei are regular and normochromatic, mitoses are scanty, necrosis is usually absent, and vascularization is florid. Exceptionally, the cytoplasm has a clear appearance. Focal mucin positivity may be present. Immunohistochemically, there is consistent positivity for neuron-specific enolase, chromogranin, and keratin. Ultrastructurally, dense-core secretory granules are found in the cytoplasm, usually in abundance.

The rate of growth of these tumors is very slow. Metastases are usually restricted to regional lymph nodes and liver, and their presence does not rule out long-term survival.It should be realized that carcinoid tumor is a generic term, which can be properly applied to any neoplasm comprising any of several types of endocrine cells known to be present in the normal human stomach.

This histogenetic diversity is already suggested by the variety of products that these tumors have been found to secrete, such as 5-hydroxytryptophan, serotonin, epinephrine, norepinephrine, somatostatin, VIP, PP, YY peptide, ACTH, beta-MSH, and alpha-1-antitrypsin.A combined morphologic, ultrastructural, and immunohistochemical approach has allowed the identification of at least two definite subtypes of gastric carcinoid.

The first is a tumor composed of G-cells (gastrinoma), analogous to its most common pancreatic or duodenal counterpart; this is usually solitary, located in the antrum, non-argentaffin and non-argyrophilic, immunoreactive for gastrin, and sometimes associated with peptic ulcer. Parenthetically, gastric G-cell tumor should be clearly separated from the disputed entity of primary G-cell hyperplasia, in which an increased number of G-cells in the antrum is accompanied by hypergastrinemia and an ulcerogenic syndrome resembling the Zollinger-Ellison syndrome.

The second form, which constitutes by far the most common type of gastric carcinoid tumor, is composed of enterochromaffin-like (ECL) cells. These lesions are usually multiple, often polypoid, and distributed throughout the fundus. They are non-argentaffin but strongly argyrophilic, nonreactive for any of the standard gastroduodenopancreatic hormones, and accompanied by diffuse hyperplasia of similar argyrophilic cells in the surrounding mucosa. Various types of smooth muscle proliferation may be present, possibly as a response to the production of basic fibroblastic growth factor. These tumors and hyperplasias usually occur on a background of atrophic gastritis with intestinal metaplasia, with or without pernicious anemia. The gastritis is usually of type A (immune) with a low incidence of H. pylori colonization. The tumors have also been seen in association with the Zollinger-Ellison syndrome, either alone or as a component of multiple endocrine neoplasia. Since the common denominator for these disorders is hypergastrinemia and since gastrin is known to have a trophic influence on ECL cells, it has been postulated that these tumors are the direct result of a continuous stimulation by gastrin against a predisposing genetic background. Regression of these lesions has been documented following the performance of antrectomy and normalization of serum gastrin levels, suggesting that some of them may represent nodular hyperplasias of ECL cells rather than true neoplasms. Indeed, an almost continuous spectrum exists between the clearly hyperplastic and the clearly neoplastic proliferation, making the dividing line between the two processes an arbitrary one.

The figure of 0.5 mm has been suggested as the dividing line between carcinoid tumors and their precursors ("precarcinoid").Solitary carcinoid tumors composed of ECL-like cells also occur; those associated with non-atrophic mucosa tend to run a more aggressive course.Although no peptide secretory product has yet been identified in ECL tumor cells, it is known that they store histamine and that histamine-producing carcinoid tumors composed of argyrophilic ECL-like cells are very common in the stomach of the South African rodent, Mastomys (Praomys) natalensis.Carcinoid tumors with atypical histologic features and adenocarcinomas with focal endocrine features are discussed in the section on gastric carcinoma.