Gastric carcinoma with argyrophilic cells: light microscopic, electron microscopic, and immunochemical study

Towards Understanding of Gastric Cancer Based upon Physiological Role of Gastrin and ECL Cells

Simple Summary

Generally, we know that cancers represent genetic changes in tumour cells, but we most often do not know the causes of cancers or how they develop. Our knowledge of the regulation of gastric acid secretion is well known, with the gastric hormone gastrin maintaining gastric acidity by stimulation of the enterochromaffin-like (ECL) cell to release histamine, which subsequently augments acid secretion. Furthermore, it seems to be a general principle that stimulation of function (which, for the ECL cell, is release of histamine) in a parallel way stimulates the proliferation of the same cell. Long-term hyperstimulation of cell division predisposes to genetic changes and, thus, development of tumours. All conditions with reduced gastric acidity result in an increased risk of gastric tumours due to elevated gastrin in order to restore gastric acidity. It is probable that Helicobacter pylori infection (the most important cause of gastric cancer), as well as drugs inhibiting gastric acid secretion induce gastric cancer in the long-term, due to an elevation of gastrin caused by reduced gastric acidity. Gastric carcinomas have been shown to express ECL cell markers, further strengthening this relationship.

Abstract

The stomach is an ideal organ to study because the gastric juice kills most of the swallowed microbes and, thus, creates rather similar milieu among individuals. Combined with a rather easy access to gastric juice, gastric physiology was among the first areas to be studied. During the last century, a rather complete understanding of the regulation of gastric acidity was obtained, establishing the central role of gastrin and the histamine producing enterochromaffin-like (ECL) cell. Similarly, the close connection between regulation of function and proliferation became evident, and, furthermore, that chronic overstimulation of a cell with the ability to proliferate, results in tumour formation. The ECL cell has long been acknowledged to give rise to neuroendocrine tumours (NETs), but not to play any role in carcinogenesis of gastric adenocarcinomas. However, when examining human gastric adenocarcinomas with the best methods presently available (immunohistochemistry with increased sensitivity and in-situ hybridization), it became clear that many of these cancers expressed neuroendocrine markers, suggesting that some of these tumours were of neuroendocrine, and more specifically, ECL cell origin. Thus, the ECL cell and its main regulator, gastrin, are central in human gastric carcinogenesis, which make new possibilities in prevention, prophylaxis, and treatment of this cancer.

Classification of tumours

Tumours are classified according to the most differentiated cells with the exception of carcinomas where a few tumour cells show neuroendocrine differentiation. In this case these cells are regarded as redifferentiated tumour cells, and the tumour is not classified as neuroendocrine. However, it is now clear that normal neuroendocrine cells can divide, and that continuous stimulation of such cells results in tumour formation, which during time becomes increasingly malignant. To understand tumourigenesis, it is of utmost importance to recognize the cell of origin of the tumour since knowledge of the growth regulation of that cell may give information about development and thus possible prevention and prophylaxis of the tumour. It may also have implications for the treatment. The successful treatment of gastrointestinal stromal tumours by a tyrosine kinase inhibitor is an example of the importance of a correct cellular classification of a tumour. In the future tumours should not just be classified as for instance adenocarcinomas of an organ, but more precisely as a carcinoma originating from a certain cell type of that organ.

Signet ring cells in gastric carcinomas are derived from neuroendocrine cells

Adenocarcinomas are malignant tumors with glandular growth and/or supposed intracellular mucin as identified by periodic acid-Schiff (PAS) positivity. Gastric signet ring cell carcinomas are classified as diffuse type. A proportion of diffuse-type adenocarcinomas have previously been suggested to be of neuroendocrine origin. In the present study we examined gastric signet ring cell carcinomas for neuroendocrine differentiation. Of 11 gastric signet ring cell carcinomas, 8 contained areas with PAS-positive signet ring cells that also were immunoreactive for one or several neuroendocrine markers: synaptophysin, chromogranin A, and histidine decarboxylase, the latter an enterochromaffin-like (ECL) cell marker. Whereas PAS positivity was located in the central cytoplasm, neuroendocrine immunoreactivity was often located as a rim surrounding an otherwise non-immunoreactive cytoplasm, presumed to represent the area with PAS-positive material. These findings indicate that signet ring cell carcinomas could be of neuroendocrine origin. We propose that signet ring cell carcinomas develop by gradual dedifferentiation from ECL cells via signet ring cells with neuroendocrine immunoreactivity toward signet ring cells where the cytoplasm mainly consists of PAS-positive material. This finding could have implications for the classification and understanding of gastric carcinogenesis.

Composite glandular-endocrine cell carcinoma of the stomach. Report of two cases with goblet cell carcinoid component

Composite glandular-endocrine cell carcinoma (CGECC) is recognized as a special type of gastric tumor composed of ordinary adenocarcinoma and neuroendocrine tumors. Goblet cell carcinoid (GCC) is a well-established type of appendiceal carcinoid, but the GCC component has not been well delineated in CGECC of the stomach. We report on two gastric CGECCs with a GCC component, analyzing the histologic components by immunohistochemistry. On initial biopsy, both cases were diagnosed as signet-ring cell carcinoma. However, the resected tumors consisted of three components: signet-ring cell carcinoma, GCC, and glandular adenocarcinoma. Although some signet-ring carcinoma cells and goblet carcinoid cells were indistinguishable by hematoxylin and eosin staining, E-cadherin immunostaining disclosed a definitive difference regarding the staining pattern in these cells. Both patients are well, with no recurrent tumor for about 10 years of follow-up. CGECC with a GCC component may have been confused with conventional adenocarcinoma with signet-ring cells. In cases of advanced signet-ring cell carcinoma with good prognosis, the possibility of such CGECC has to be considered.

Neuroendocrine differentiation of periodic-acid Schiff and Alcian blue-negative signet-ring cell-like cells and tubular adenocarcinoma cells within a gastric cancer

A case of a Borrmann type 2 advanced gastric cancer with endocrine differentiation is described. Histologically, the cancer was either composed of cells arranged in a tubular pattern or formed solid nests of various sizes. The tubular pattern was composed of a moderately differentiated tubular adenocarcinoma. The histology showed partial carcinoid tumor-like features. Cancer cells inside solid nests had a signet-ring cell-like appearance. Periodic-acid Schiff (PAS) staining was positive in the cytoplasm of a few of the cells found in the tubular pattern and in the mucus in some lumens and on the apical surface of cells in some lumens, but PAS did not stain cancer cells in the solid nests. Neither cancer cells nor mucus in the lumens were stained with alcian blue. All cancer cells were strongly positive for Grimelius silver stain, and most of the cancer cells stained positively for chromogranin A. Electron microscopic examination showed electron dense neuroendocrine granules in the cytoplasm of cancer cells. Cancer cells were stained positively for pancytokeratin, cytokeratin 8/18 and carcinoembryonic antigen. Muc 1 mucin glycoprotein staining was positive along the cell surfaces of cancer cells, but Muc 2, 5AC and 6 stainings were negative, although Muc 3 stained positively in the cytoplasm of a few cancer cells. The present case is a gastric tubular adenocarcinoma with Muc 1-positive, neutral- and acid mucin-negative signet-ring cell-like cells, which is associated with neuroendocrine differentiation.

CEA-producing mucin-negative gastric signet-ring cell carcinoma with neuroendocrine markers: a case report

Biopsy and autopsy materials excised from a 69-year-old woman were investigated. Serum carcinoembryonic antigen (CEA) showed a high value of 955 ng/mL. A plateaulike tumor was located in the gastric cardia and fundus to the entire gastric body. It showed severe proliferation and infiltration from the mucosa to the serosa. The tumor was comprised of signet-ring cells and poorly differentiated adenocarcinoma cells, which spread into the submucosa of the pylorus, duodenum, and jejunum. Signet-ring cells had a large, eccentric vesicular nucleus and a pale cytoplasmic inclusion. Poorly differentiated adenocarcinoma cells had a pleomorphic nucleus, small eosinophilic nucleolus, and abundant eosinophilic cytoplasm. Both neoplastic cells were positive for CEA, epithelial membrane antigen, Leu-7 (CD57), and neuron-specific enolase, and were negative for cytokeratin, vimentin, and periodic acid-Schiff, Alcian blue, and mucicarmine stains. Electron microscopy showed endocrine granules with a limiting membrane measuring approximately 238 nm in diameter in the cytoplasm. The authors diagnosed this patient as having mucin-negative gastric signet-ring cell carcinoma with neuroendocrine markers, which is suggested to exist among poorly differentiated adenocarcinoma, undifferentiated carcinoma, and signet-ring cell carcinoma.

Neuroendocrine carcinoma of the stomach with extensive somatostatin immunoreactivity

Upper gastrointestinal tract neuroendocrine tumors producing predominantly somatostatin have thus far been described only in the duodenum; their characteristic features include the frequent presence of psammoma bodies (psammomatous somatostinomas), and the association with von Recklinghausen's neurofibromatosis. Gastric neuroendocrine tumors, on the other hand, tend to display immunoreactivity to serotonin but may include small subpopulations producing gastrin, motilin, pancreatic polypeptide, and somatostatin. In this report we describe a neuroendocrine carcinoma of the stomach with rapidly fatal outcome, displaying neurosecretory granules by electron microscopy and immunoreactivity to pan-neuroendocrine markers, ie, chromogranin and neuron-specific enolase. The only neuroendocrine regulatory peptide detected in the tumor was somatostatin, identified by immunohistochemistry in the majority of neoplastic cells. In contrast with duodenal somatostinomas, there were no psammoma bodies and no demonstrable association with von Recklinghausen's neurofibromatosis. To our knowledge this appears to be the first report of a malignant neuroendocrine tumor with diffuse somatostatin immunoreactivity.

Neuroendocrine tumors of the gastrointestinal tract

Neoplastic proliferations of neuroendocrine cells (NE) may occur throughout the entire GI tract but affect particularly appendix and ileum ("midgut carcinoids"), rectum ("hindgut carcinoids"), as well as stomach and the duodenum ("foregut carcinoids"). Only more exceptionally, they arise in the esophagus, jejunum and colon. The NE tumors encompass a heterogeneous gross and microscopic structural spectrum, ranging from inconspicuous microproliferations ("mucous membrane nevi") to bulky tumor masses. Their growth patterns are usually characteristic and easily recognized. In doubtful cases their NE differentiation becomes established by a characteristic silver affinity, by the ultrastructurally observed presence of characteristic "endocrine" secretion granules, and by immunohistochemically detectable occurrence of "pan-NE markers" (neuron-specific enolase, chromogranins, and synaptophysin), biogenic amines (mainly serotonin), and neurohormonal peptides. Foregut carcinoids usually contain serotonin, gastrin, and somatostatin, midgut carcinoids often only serotonin and tachykinins, whereas the hindgut carcinoids as a rule are multihormonal with a wide spectrum of hormonal peptides, including even insulin. Most GI NE tumors are found in the appendix (50%) and the ileum (30%). Practically all (98%) of the appendiceal NE tumors are benign. They have recently been proposed as arising from apparently Schwann-cell-related NE cells in the submucosa, whereas the ileal--and probably also all the other non-appendiceal NE tumors--are derived from the totipotential cells in epithelial crypts of the mucosa. Among the ileal NE neoplasms a large number can metastasize and result in a fatal outcome. The ability to metastasize is related to the size and to the multiplicity of the primary tumors at the time of initial diagnosis and, to some extent, to their histopathologic growth pattern. Now, some relationship between the prognosis and the cytochemically assessed nuclear DNA content of the NE tumor cells has also been established; not less than about 1/4 to 1/3 seem to be aneuploid. Almost 90% of the rectal carcinoids are benign. Exceptionally, a highly malignant NE neoplasms can arise from the colon/rectum--as well as from the esophagus--composed of NE cells of small and intermediate size. The NE tumors of the stomach are often composed of ECL (enterochromaffin-cell-like) cells; such ECL cell carcinoids are related to atrophic gastritis with pernicious anemia; experimentally, they can be induced by hypergastrinemia in rats. Duodenal carcinoids often contain psammoma bodies and can be associated with neurofibromatosis.

Characterization of four main cell types in gastric cancer: foveolar, mucopeptic, intestinal columnar and goblet cells. An histopathologic, histochemical and ultrastructural study of "early" and "advanced" tumours

Gastrectomy specimens of 148 gastric cancers, 40 of them being intramucosal or microinvasive, 27 penetrating the submucosa and 81 invading the muscularis propria, with or without involvement of the serosa and perigastric tissues, have been investigated with conventional histopathologic techniques, mucin histochemistry and electron microscopy to characterize the various lines of tumour cell differentiation and to correlate these with the histologic patterns of tumour growth. More or less differentiated intestinal columnar, intestinal goblet, gastric foveolar or mucopeptic cells were recognized in most tumours, of glandular, diffuse or mucoid type. Although simultaneous expression of more than one cell type into the same tumour occurred very frequently, intestinal columnar cells were more prominent in tubular adenocarcinomas, goblet cells (especially of colorectal type) in mucoid cancers, mucopeptic cells in diffuse cancers of invasive desmoplastic type and foveolar cells in diffuse cancers of intramucosal signet-ring cell type. In general, an increased tendency to foveolar cell differentiation and a reduced tendency to mucopeptic differentiation has been found in intramucosal cancers as compared to invasive cancers. It is concluded that the type of tumour cell differentiation, which might have some influence on the natural history of gastric cancer, is better related with more defined tumour subtypes than with the usually recognized glandular or diffuse patterns.

Evidence for partial exocrine acinar differentiation in experimentally induced pancreatic ductal/ductular cell tumors

The pancreatic carcinomas induced in Syrian hamsters by a nitroso compound are of a ductal/ductular cell type. Electron microscopic examination of such tumors has revealed the presence of an occasional isolated acinar cell within the tumor. Based on their cellular characteristics, these acinar cells seem to have derived from ductular cell precursors. When we used a monoclonal antibody which specifically recognizes hamster acinar cells, a larger number of cells bearing acinar cell membrane markers were found in many tumors by an indirect immunofluorescence technique. Since most of these positively reacting cells did not exhibit the characteristic cytological features of acinar cells, such as rough endoplasmic reticulum and zymogen granules, differentiation of precursor cells to acinar cells may possibly occur at the cell membrane level. The presence of a few acinar cells within exocrine pancreatic tumors implies that acinar differentiation or retrodifferentiation can occur in pancreatic neoplasms.

Neoplastic nature of argyrophil cells in urachal adenocarcinoma

The histological, histochemical and electron microscopic features of the metastatic tumors of an urachal adenocarcinoma, were presented. Metastatic tumor nodules in the lungs and brain as well as the primary tumor showed tubular adenocarcinoma containing many argyrophil cells. Immunoperoxidase examination revealed three kind of endocrine cells which contained different endocrine hormones. Electron microscopic examination showed small, round endocrine granules in the endocrine cells and desmosome-like complexes in between these cells and the adjacent glandular neoplastic cells. These findings suggested that the endocrine cells were neoplastic in nature and originated from primitive neoplastic cells as well as glandular neoplastic cells.

Argyrophil cells in the urachal epithelium and urachal adenocarcinoma

Urachal adenocarcinoma, normal urachus, and urinary bladder were studied by histochemical methods and electron microscopy. Many argyrophil cells were found in urachal adenocarcinoma and urachal epithelium. Autofluorescence and immunoperoxidase examinations showed that the argyrophil cells possessed serotonin, glucagon, and secretin. Some of the carcinoma cells and urachal epithelial cells contained fairly large amount of mucosubstances. On the other hand, only a few argyrophil cells and very weakly PAS positive cells were observed in the urinary bladder mucosa. This study showed that there were close similarities in the histochemical and electron microscopical features between the urachal carcinoma and urachal epithelium, and suggested that the undifferentiated stem cells were able to differentiate to both glandular and endocrine cells.

Neurohormonal peptides in endocrine tumors of the pancreas, stomach, and upper small intestine: I. An immunohistochemical study of 27 cases

Preliminary observations have indicated the existence of characteristic spectra of gastroenteropancreatic (GEP) neurohormonal peptides in endocrine tumors arising in foregut, midgut, and hindgut derivatives. In order to further explore this feature of GEP endocrine neoplasms, islet cell tumors from 14 patients were studied, as were endocrine tumors of the stomach, duodenum, and upper jejunum from 6, 5, and 2 patients, respectively. All tumors were examined immunohistochemically with antisera raised against islet hormones [insulin, somatostatin, glucagon, pancreatic polypeptide (PP)], peptides of the gastrin family [gastrin, cholecystokinin (CCK)], peptides of the secretin family [secretin, vasoactive intestinal peptide (VIP)], and substance P, neurotensin, leu-enkephalin, beta-endorphin, motilin, calcitonin, and ACTH. In addition, an ultrastructural investigation was made. Whenever possible, the immunohistochemical observations were correlated with the clinical manifestations and with the results of radioimmunochemical determination of GEP neurohormones in the blood. The pattern of immunoreactive neurohormonal peptides and the clinical picture were those to be expected in endocrine tumors arising in foregut derivatives. Some principles are proposed for the classification of GEP endocrine tumors on the basis of their histopathologic growth pattern, their spectrum of neurohormonal peptides, and their clinical manifestations.