Mucins and carcinoid tumours

Gastrin and Gastric Cancer

Gastric cancer although occurring in reduced frequency is still an important disease, partly because of the bad prognosis when occurring in western countries. This decline in occurrence may mainly be due to the reduced prevalence of Helicobacter pylori (Hp) infection, which is the most important cause of gastric cancer. There exist many different pathological classifications of gastric carcinomas, but the most useful seems to be the one by Lauren into intestinal and diffuse types since these types seldom transform into the other and also have different epidemiology. During the nearly 30 years that have passed since the groundbreaking description of Hp as the cause of gastritis and gastric cancer, a continuous search for the mechanism by which Hp infection causes gastric cancer has been done. Interestingly, it is mainly atrophic gastritis of the oxyntic mucosa that predisposes to gastric cancer possibly by inducing hypoacidity and hypergastrinemia. There are many arguments in favor of an important role of gastrin and its target cell, the enterochromaffin-like cell, in gastric carcinogenesis. The role of gastrin in gastric carcinogenesis implies caution in the long-term treatment with inhibitors of gastric acid secretion inducing secondary hypergastrinemia, in a common disease like gastroesophageal reflux disease.

Detection of chromogranin A in human gastric adenocarcinomas using a sensitive immunohistochemical technique

Neuroendocrine cells are often disclosed in human gastric adenocarcinomas and may be recognised by their immunoreactivity towards chromogranin A. However, in dedifferentiated neuroendocrine tumour cells, the chromogranin A content may be reduced making it difficult to detect with conventional immunohistochemical methods. We therefore used a sensitive signal amplification technique in order to evaluate chromogranin A immunoreactivity and thus neuroendocrine differentiation in 40 gastric adenocarcinomas. Neuroendocrine cells were visualised by means of a monoclonal chromogranin A antibody and the avidin-biotin peroxidase complex technique, without and with addition of tyramide signal amplification. Double immunohistochemistry towards chromogranin A and Ki-67 were used to disclose proliferation in the neoplastic cells. A marked increase in the number of carcinomas containing chromogranin A-immunoreactive neoplastic cells was noted when applying the tyramide signal amplification technique. In addition, the number of immunoreactive cells within each tumour increased, and in some cases almost all the neoplastic cells became immunoreactive. Chromogranin A-immunoreactive tumour cells showing signs of proliferation were found in the majority of these carcinomas. In conclusion, we have disclosed widespread immunoreactivity towards chromogranin A in a proportion of gastric adenocarcinomas when enhancing the signal with tyramide signal amplification. Neuroendocrine differentiation is thus a common finding in gastric carcinomas when using sensitive methods.

Histochemical and ultrastructural analyses of glandular differentiation in typical carcinoid tumor of the hindgut

Adenomatous differentiation of typical carcinoid tumors was examined by histochemical and ultrastructural studies on 33 cases of typical carcinoids of the hindgut. Of these 33 carcinoids, 12 (36%) showed a tubular and/or acinar pattern with production of mucus as a minor component. A few tumor cells with mucous globules were scattered among tubules in these carcinoids. Ultrastructurally, microvilli were seen along the luminal surface of tubules, with both numerous mucous globules in the supranuclear area and endocrine granules in basal sites of the same cells. These results indicate that even in typical carcinoid tumors, certain tumor cells have the features of goblet cells or the open type of endocrine cells. The findings of both mucous globules and endocrine granules in the same single cells indicate a close relationship between endocrine cells and mucus-producing and/or tubule-forming cells. It is concluded that pluripotential cells producing carcinoid tumors might be able to differentiate into three types of tumor cells: (i) endocrine cells without microvilli or mucus production; (ii) cells with microvilli and no mucus product; and (iii) mucus-containing cells with microvilli.

The enterochromaffin-like (ECL) cell. Physiological and pathophysiological role

Histamine has a central role in the regulation of gastric acid secretion. This histamine is produced by and released from the enterochromaffin-like (ECL) cell which accordingly has a key-regulatory role in the oxyntic mucosa. Gastrin and the vagal nerves stimulate the formation and release of histamine from the ECL cell. Moreover, gastrin and the vagal nerves also stimulate the proliferation of the ECL cell. An increased ECL cell density may partly explain the increased acid secretion in patients with duodenal ulcer, particularly in patients with Zollinger-Ellison syndrome. The reduced potency of histamine-2 blockers in patients with Zollinger-Ellison syndrome is probably due to increased histamine release by an elevated ECL cell mass. Prolonged and profound hypergastrinemia may lead to ECLomas. Moreover, a proportion of diffuse gastric carcinomas may originate from ECL cells.

Adeno-carcinoid or amphicrine tumors of the middle ear a new entity?

The clinicopathological, ultrastructural and immunohistochemical characteristics of four primary tumors of the middle ear are reported. These neoplasms showed a striking, heterogeneous aspect ranging from solid-trabecular (Type I) to tubulo-glandular (Type II) growth patterns. Secretory activity of the tumor cells was evaluated by immunohistochemistry and electron microscopy. Based on these procedures, three cell types were found, mainly limited to tumors with a tubulo-glandular (Type II) growth pattern. Most frequent were B-cells with an abundant pale cytoplasm containing neuroendocrine granules, both cytokeratin and vimentin as well as several endocrine marker substances. Less frequent were A-cells, which are slender, darkly staining and line the glandular lumina. They showed exocrine activity only and stained strongly with a polyclonal cytokeratin antibody. Finally, least frequent were amphicrine cells, which were characterized by both lumina and neuroendocrine granules in their cytoplasm and were interpreted as the link between A and B cells. Although this morphological description closely resembles that of carcinoids and adenocarcinoids of the respiratory tract and gut, the clinical behaviour of these middle ear tumors nevertheless seems different, with no recurrence or metastasis after a follow-up of 1 to 14 years (median 78 months). Therefore, some authors suggest that these tumors should be classified as middle ear adenomas or adenomatous tumors. However, we strongly feel that these tumours represent a distinct entity and can be classified as adenocarcinoids or amphicrine tumors, i.e. demonstrating both exocrine and endocrine activities. Further work is required to evaluate the exact proportion of neuroendocrine and amphicrine tumors in the heterogeneous group of adenomas and in the rarely described group of adenocarcinomas.

Lectin expression in carcinoid tumours of the gastrointestinal tract

The binding of peroxidase-conjugated Dolichos biflorus (DBA), Triticum vulgaris (WGA), Canavalia ensiformis (Con A), Arachis hypogaea (PNA), Lotus tetragonolobus, and Bandeiraea simplicifolia I (BSAI) to gastrointestinal carcinoid tumours was studied. The results indicate that carcinoid tumour cells express certain carbohydrates similar to those present in the adjacent surface epithelium. The differences in the lectin-binding properties of carcinoid tumours of different sites of the gastrointestinal tract are closely related to the regional differences in the lectin binding of adjacent surface epithelium. These observations therefore form a useful basis for further studies in the application of lectin histochemistry to elucidate the histogenesis of carcinoid tumours.

Mixed crypt cell carcinoma. A clinicopathological study of the so-called 'goblet cell carcinoid'

The clinicopathological features of six appendix and five bowel tumours with features of the so-called 'goblet cell carcinoid' are described. By light microscopy, these tumours were composed predominantly of mucous cells, together with variable proportions of endocrine and Paneth cells. Immunohistochemical and ultrastructural study confirmed this impression and no amphicrine cells were seen. The clinical course of all cases arising in the bowel, and three out of six appendix tumours was characterised by an aggressive behaviour with the development of widespread lymphatic and often intraperitoneal metastasis, but liver metastasis occurred in only one instance. We conclude, both from this study and from a review of the literature, that the 'mixed crypt cell carcinoma' forms a distinct clinicopathological entity justifying separate classification from adenocarcinoma and carcinoid tumour.

Bronchial adenocarcinoid tumor metastatic to skin

A pulmonary neoplasm, evident initially as a metastatic nonpruritic skin rash in a 51-year-old man, progressed during a period of four months, leading to the patient's death. Histologic and histochemical studies of the skin metastasis, which were confirmed by transbronchial biopsy, demonstrated an adenocarcinoid tumor. Further ultrastructural studies of the skin metastasis showed that many tumor cells contained neurosecretory granules, although histochemical analyses had revealed the presence of only a few such tumor cells. Furthermore, in some cells both mucin and neurosecretory granules were present in the cytoplasm, confirming a previous observation in normal human segmental bronchi. These findings support the endodermal origin of such neoplasms.

Carcinoid tumors of the ileum

Thirty patients with carcinoid tumors of the ileum over a recent 10-year period have been analyzed. Seventeen patients were symptomatic and 13 others were found to have tumors incidentally at autopsy or celiotomy. Patients with symptoms almost invariably had metastatic disease, yet preoperative diagnosis was rarely achieved. Arteriography in five patients with intestinal angina demonstrated encasement, kinking, and irregularity of mesenteric branches due to nodal metastasis. In five patients, each with liver metastasis, the classic carcinoid syndrome developed. Multiple primary carcinoid tumors were found in 9 of 30 patients (30 percent); 14 had an associated second malignant neoplasm (47 percent), most frequently colorectal carcinoma. En block surgical excision was the only effective therapy. Despite a prolonged natural history, the 5-year actuarial survival rate from the date of diagnosis was only 31 percent.

Adenocarcinoid of the vermiform appendix

Four cases of adenocarcinoid of the appendix were studied. Two tumours were found among 28 cases primarily diagnosed as appendiceal carcinoids. They showed characteristic histological structures with features of both a conventional carcinoid tumour and a mucinproducing adenocarcinoma with goblet cells. All tumours were small and ill-defined; three were associated with fibrous obliteration of the appendiceal lumen. All were diagnosed incidentally by the pathologist in appendices removed "en passant" or because of acute appendicitis. Three of the tumours appeared well differentiated with a low degree of malignancy similar to that of the conventional carcinoid tumour. In one case however, the tumour was less differentiated with atypical foci and a high mitotic count and had metastasised to peritoneum and both ovaries.