Gastric carcinoid

The prodrugs are unstable in the presence of acid and therefore must be administered as an enteric-coated preparation or as a buffered suspension. Pantoprazole is also available in an intravenous formulation. The most commonly reported side effects are diarrhea and headache. Hypergastrinemia has been noted as a reaction to the marked reduction in acid secretion. Gastric carcinoid tumors have developed in rats but not in mice or in human volunteers, even after long-term use. 

Histamine is formed by decarboxylation of the amino acid l -histidine, a reaction catalyzed in mammalian tissues by the enzyme histidine decarboxylase. Once formed, histamine is either stored or rapidly inactivated. Very little histamine is excreted unchanged. The major metabolic pathways involve conversion to /V-methylhistamine, methylimidazoleacetic acid, and imidazoleacetic acid (IAA). Certain neoplasms (systemic mastocytosis, urticaria pigmentosa, gastric carcinoid, and occasionally myelogenous leukemia) are associated with increased numbers of mast cells or basophils and with increased excretion of histamine and its metabolites. 

There has been concern about the potential for proton pump inhibitors to cause enterochromaffin-hke cell hyperplasia, gastric carcinoid tumors and gastric cancers, colorectal polyps and adenocarcinoma, atrophic gastritis, and intestinal metaplasia in patients with H. pylori infection, and bacterial overgrowth. 

A gastric carcinoid tumor, detected during long-term anti-ulcer therapy with a histamine receptor antagonist and proton pump inhibitors, has been reported (34). 

Haga Y, Nakatsura T, Shibata Y, Sameshima H, Nakamura Y, Tanimura M, Ogawa M. Human gastric carcinoid detected during long-term antiulcer therapy of H2 receptor antagonist and proton pump inhibitor. Dig Dis Sci 1998 43(2) 253-7. 

A gastric carcinoid tumor was found in a man of 62 taking ranitidine (22). The dosage had been unusually high and there was pre-existing chronic renal insufficiency as well as diabetes, but the tumor was similar in type to that seen in animals it was successfully removed by partial gastrectomy and did not recur. 

Rao SS, Nayak KS, Swarnalata G, Goyal DN, Rao KP, Mitros FA. Gastric carcinoid associated with ranitidine in... 

The proton pump inhibitors are usually well tolerated however, potential adverse effects include headache, dizziness, somnolence, diarrhea, constipation, and nausea. The frequency of adverse events appears to be similar to that seen with the H2-receptor antagonists. Concern and controversy regarding the safety of therapy with a proton pump inhibitor are based on the proton pump inhibitor s ability to cause hypergastrinemia and gastric carcinoid tumors in rats. After nearly a decade of experience with the proton pump inhibitors, gastric carcinoid tumors have not been directly linked to omeprazole use in humans. ... 

B11. Borch, K., Renvall, H., Kullman, E., and Wilander, E., Gastric carcinoid associated with the syndrome of hypergastrinemic atrophic gastritis. J. Surg. Pathol. 11,435-444 (1987). 

Thomas RM, Baybick JH, Elsayed AM, Sobin LH. Gastric carcinoids An immunohistochemical and clinicopathologic study of 104 patients. Cancer. 1994 73 2053-2058. 

The positive staining for AE1/AE3 and CAMS.2 that is seen in gastric carcinoids can help distinguish them from secondary involvement of the gastrointestinal tract by other neuroendocrine tumors such as pheochromocytoma and retroperitoneal paraganglioma. 

Bordi C, Yu JY, Baggi MT, et al. Gastric carcinoids and their precursor lesions. A histologic and immunohistochemical study of 23 cases. Cancer. 1991 67 663-672. 

Azzoni C, Doglioni C, Viale G, et al. Involvement of BCL-2 oncoprotein in the development of enterochromaffin-like cell gastric carcinoids. Am Surg Pathol. 1996 20 433-441. 

INCREASED PROLIFERATION OF MAST CELLS AND BASOPHILS GASTRIC CARCINOID TUMORS... 

Omeprazole (Prilosec) Inhibits H+/K+ ATPase (proton pump) of parietal cell. Thus, reduces acid secretion. Reflux esophagitis, hypersecretory states. Few side effects. Constipation. Causes gastric carcinoid tumors in rats after prolonged use. 

Fig. 19.1. a Sonographic features of a gastric carcinoid. A round-shaped hypoechoic tumor is demonstrated. Wall stratification is not demonstrated clearly in this figure, b Color Doppler ultrasound shows the rich vascularity of the tumor, c Contrast-enhanced ultrasound of the tumor also reveals the rich blood perfusion... 

Oates, J. A. and Sjoerdsma, A., An unique syndrome associated with secretion of 5-hydroxytryptophan by metastatic gastric carcinoids. Am. J. Med. 32, 333 (1962). 

The tumor is histamine secreting and does not metastasize, which renders it closely comparable to the human type I gastric carcinoid tumor. If untreated, animals develop duodenal ulcers, which either bleed or perforate, resulting in demise of the tumor carrier on an acute basis. The tumor could be successfully... 

Distribution of the 13,715 carcinoid tumors contained by the ERG, TNCS, and the SEER file (1950-1999) by organ site. The dominant site for carcinoid development is the gastrointestinal system. Gastric carcinoids constitute 4.1% of all carcinoid tumors. 

Three patterns of gastric carcinoid (ECL cell) tumor have been proposed (a) argyrophilic carcinoids arising in type A chronic atrophic gastritis (chronic atrophic gastritis/A), (b) argyrophilic ECL cell carcinoids in MEN-1-ZES, and (c) sporadic argyrophil carcinoids. 

The characteristic features of the different types of gastric carcinoid tumors. 

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