Mucin producing carcinoid tumours of the vermiform appendix.

Six cases of an unusual mucoid variant of carcinoid tumour of the appendix are reported. These lesions are small, detected incidentally, and carry a good prognosis. Their histological features are distinctive and differ from those of ordinary carcinoid tumours and adenocarcinoma. They have been confused with adenocarcinoma, sometimes resulting in radical surgery. Surgery beyond appendicectomy is probably unwarranted in these cases. The mucin secreted by goblet cells of the normal mucosal epithelium and by the cells of these carcinoid tumours have certain histochemical similarities.     

Mucins and carcinoid tumours

Mucin was demonstrated in 11 of 16 carcinoid tumours of usual histological appearances. The mucin was characterized histochemically and shown to be similar to that which is produced in the gastrointestinal as well as the respiratory tract. This relative ubiquity of mucin in carinoid tumours has not hitherto been appreciated and more obviously "mixed" tumours have been regarded as rareties. The importance of these findings with respect to the neural crest theory of origin of enterochromaffin cells is discussed.     

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.     

The histogenesis of appendiceal carcinoid tumours

Twenty-two appendiceal carcinoid tumours, comprising 10 classical carcinoids, six tubular carcinoids and six goblet cell carcinoids were examined by histochemistry and immunohistochemistry. All of the tumours showed evidence of neuroendocrine differentiation. Classical carcinoids were invariably intimately associated with S-100 protein positive cells, supporting an origin from sub-epithelial neuroendocrine cells. Both tubular and goblet cell carcinoids expressed cytoplasmic mucin and immunoglobulin A, and neither were associated with S-100 protein positive cells. These observations suggest that tubular and goblet cell carcinoids are derived from epithelial crypt stem cells.     

Lack of C-erbB-2 protein expression in pulmonary carcinoid tumours.

To determine if amplification of the C-erb-B2 proto-oncogene could be correlated with prognosis in carcinoid tumours, 49 pulmonary carcinoid tumours (26 typical, 23 atypical) were examined using a polyclonal antibody to the C-terminal peptide of the C-erb-B2 protein sequence. No C-erb-B2 gene product could be shown: the demonstration of C-erb-B2 does not seem to help, therefore, in determining diagnosis or prognosis in pulmonary carcinoid tumours.     

Pulmonary carcinoid tumours: a comparative regional study.

Twenty-two pulmonary carcinoid tumours (18 central, 4 peripheral) were seen in this department over an 11-year period. The majority of the tumours displayed a mixed pattern on microscopic examination, and cell-nest formation was a prominent feature in sixteen. The findings are at variance with the results of a similar series reported from Japan and suggest that there is regional variation in the tumour pattern of pulmonary carcinoids. Various aspects of the histopathology are discussed, and a causal relationship between ossification of bronchial cartilage in these tumours and locally produced calcitonin is postulated.     

The histogenesis of carcinoid tumours of the rectum

`Carcinoid'' tumours of the rectum have been described which are classified on histological appearances into three main varieties: `true'' carcinoid or argentaffinoma, `atypical'' or non-argentaffin carcinoid, and `composite carcinoid. The histogenesis of these tumours is discussed and it is suggested that non-argentaffin carcinoids of the rectum have an essentially similar histogenesis to certain tumours of the lung, pancreas, and gastrointestinal tract. The difference in growth, pattern, and staining reactions are a reflection of differing directions and levels of differentiation of the parent epithelium. The functional implications of this hypothesis are discussed.     

Argentaffin and non-argentaffin carcinoid tumours of the appendix

Tumours of the vermiform appendix were studied. The majority proved to be carcinoid tumours of the usual argentaffin-positive type but a substantial minority, generally tumours of minute size, were found to have a somewhat different histological pattern and were argentaffinnegative. Some contained argyrophil granules. The non-argentaffin tumours are considered to form a subgroup of carcinoid tumours.     

Carcinomas and carcinoid tumours of the appendix in a district general hospital.

In a retrospective series of 40 appendiceal tumours occurring over a 10-year period, 30 were carcinoid tumours of classical histological pattern, five were adenocarcinomas, and two were tumours intermediate in pattern between carcinoid and carcinoma. The remaining three tumours were secondaries from primary colonic tumours. The implications of the findings are discussed.     

Histamine metabolism in patients with foregut carcinoid tumours

The urinary excretion of the histamine metabolite, tele-methylimidazoleacetic acid (MemAA), was measured in 15 patients with foregut carcinoid tumours (5 ECLomas, 4 gastric carcinoids of the mixed type and 6 bronchial carcinoids), High levels were related to tumour burden and presence of the foregut carcinoid syndrome. Control of symptoms was either achieved by octreotide in combination with blockade of histamine receptors or by hyperthermic liver perfusion chemotherapy. MemAA served as an exellent tumour marker for diagnosis and guidance of therapy.This work was supported by grants from the Swedish MRC (5520), Jubileumsklinikens Cancer Research Fund and Landstinget, Östergötland.     

Nonantral gastric carcinoid tumours associated with hypergastrinaemia

Nonantral gastric carcinoid tumours in association with pronounced hypergastrinaemia are reported in 6 patients. It is suggested that the hypergastrinaemia, as a result of lack of a negative acid feedback inhibition in an achlorhydric stomach, promoted the tumour development, possibly initiated by action of carcinogenic nitrosamines, in the gastric juice.     

Antibody probes in the diagnosis of anaplastic tumours. I. Malignant round cell tumours

The introduction of hybridoma technology has rapidly expanded the scope of immunohistological analysis in the identification of anaplastic malignant tumours. High affinity antibodies now allow the detection of a wide range of tissue-specific antigens so that anaplastic tumours can be accurately classified without the need for costly and often unrewarding, time-consuming ancillary investigations such as electron microscopy, cell culture and chromosomal studies. This review examines the application of a panel of commercially available antibodies of proven specificity, chosen to allow separation of the various entities considered in the differential diagnosis of anaplastic round cell tumours. The specifications of the antibodies are discussed and details of selected cases are provided to illustrate the role of such tissue-specific antibodies as diagnostic probes.     

Histochemistry and fine structure of bronchial carcinoid tumours

Summary The histological, histochemical and ultrastructural features of six carcinoid tumours of the larger bronchi are described. Electron microscopy and methods known to stain endocrine cell granules selectively allowed differentiation of three types of endocrine cells. Electron microscopy revealed that two of these cell types were similar to endocrine cells normally found in the pulmonary epithelium of human foetuses. These cells had small, round membrane-bound secretory granules of uniform size and shape, or much larger, round secretory granules, tightly surrounded by a membrane and almost homogeneous in appearance. The secretory granules of the third cell type were characterized by large polymorphic secretory granules, vesiculated or tightly surrounded by a membrane. These cells were reactive to staining with the argentaffin silver method and were quite similar to the enterochromaffin cell known from the digestive tract. Scattered mastocytes which reacted to some of the granule staining methods were easily identified by electron microscopy.