Prostaglandins and carcinoid tumours

Prostaglandins and the gastrointestinal mucosa: are they important in its function, disease, or treatment?

In 1971 interest in the role of prostaglandins in the gastrointestinal tract was stimulated by the publication of two hypotheses--that aspirin damaged the gastric mucosa by inhibiting prostaglandin synthesis (1) and that cholera toxin caused diarrhea by stimulating it (2). Subsequent research into the gastrointestinal actions of prostaglandins has been considerable and now impinges on clinical practice. This paper reviews the involvement of prostaglandins and related compounds in mucosal protection, in ulcer healing, in diarrhea, and in gastrointestinal inflammation, with particular reference to the growing body of human data.

Carcinoids and the carcinoid syndrome

The many manifestations of carcinoids will continue to puzzle and intrigue surgeons. Because these are dynamic tumors which produce multiple hormones with many potential side effects, an aggressive surgical debulking of them is advocated. Even in the presence of metastatic disease, some long-term survival can be anticipated. The most debillitating aspect of this tumor to the patient is the carcinoid syndrome. The symptoms occur erratically and are often not well controlled by presently available medication. Although metastatic disease present at diagnosis is most commonly seen with jejunoileal carcinoids, colorectal carcinoids appear to be the most lethal tumors. However, they are rarely associated with the symptoms of carcinoid syndrome. Carcinoids may often be associated with other types of tumors, some of which are known to produce their own hormones. Survival of the patients seems to be related to their other tumor type rather than the primary carcinoid. The clinician should be aware of the strong association of carcinoids with peptic ulcer disease. The ulcer diathesis is probably related to ectopic histamine production and can usually be controlled by cimetidine and antacids, although surgical intervention may be required.

Canine hepatic carcinoids

In 110 primary hepatic neoplasms in the dog, 15 carcinoids were diagnosed. Diffuse involvement of all liver lobes with severe hemorrhage and necrosis was seen in all cases. The neoplasms had three distinct histologic patterns: solid nests, cords or ribbons; and an alveolar pattern with rosettes. In all three groups there was fibrovascular stroma that was hyalinized, mineralized, and thick in some places. The neoplastic cells were relatively uniform, polygonal to spindle-shaped, with eosinophilic, granular cytoplasm and vesiculated nuclei. Mitotic activity varied among the three groups. Argyrophilia was seen in all specimens stained with modified Grimelius stain. Metastasis occurred in 14 of 15 dogs (93.3%); the peritoneal wall and adjoining lymph nodes were the most common sites.

Prostaglandins and serotonin: nonpeptide diarrheogenic hormones

Prostaglandins and serotonin are vasoactive compounds with profound effects on the gastrointestinal tract. Both cause inhibition of gastric acid secretion (although serotonin stimulates gastric pepsin secretion), stimulation of intestinal motility, and conversion of small intestinal mucosa from absorption to secretion of water and electrolytes. Their effects on pancreatic and biliary function are still not clear. Although prostaglandins appear to elicit their effects primarily by a paracrine mode of action, and serotonin is primarily a neurotransmitter (neurocrine), it is clear that even under normal conditions both can function as humoral agents. For example, we have shown that serotonin plays a physiologic role as a humoral inhibitor of gastric acid secretion. However, the effects of these agents become more pronounced in patients with humorally mediated diarrheogenic syndromes. Serotonin (and related indoles, particularly 5-hydroxytryptophan) has been firmly implicated as a cause of diarrhea in patients with carcinoid syndrome; our recent studies suggest that the diagnosis can be more effectively made by measuring circulating immunoreactive serotonin concentrations than urinary excretion of 5-HIAA; that some circulating serotonin escapes hepatic inactivation and, thus, large intestinal tumors can cause carcinoid syndrome in the absence of hepatic metastases; and that large amounts of serotonin are produced by some noncarcinoid diarrheogenic tumors, including medullary carcinomas of the thyroid and tumors associated with the WDHA syndrome. A large number of tumors of probable neural crest origin, including medullary thyroid carcinoma, carcinoids, and tumors associated with the WDHA syndrome, secrete large amounts of prostaglandins, particularly PGE2. The clinical response of at least some of the patients harboring these tumors to inhibitors of prostaglandin synthesis (particularly indomethacin) suggests that prostaglandins play a role in the etiology of these diarrheogenic syndromes.

Gastrointestinal carcinoids: extrahepatic metastases and symptomatology following resection

Of 49 patients with midgut and hindgut carcinoids, second primary distinct carcinomas occurred in 12. The most aggressive carcinoids were the 24 that arose in the distal small bowel and cecum. Of the patients affected, 15 had lymph node metastases and eight had liver metastases at the time of diagnosis. That only five patients were completely relieved of symptoms following resection was partially explained by autopsy findings in 15 patients, six of whom had metastatic extra-abdominal carcinoid without liver metastases (most commonly, bone metastases).

Diagnosis and management of gastric carcinoid tumour with hepatic metastases

The gastric carcinoid tumour is a rare variety of carcinoid characterized by atypical production of 5-hydroxytrytophane rather than serotonin. In our case it is likely that other polypeptides are the source of symptoms, though these are as yet unidentified. Since surgery was not feasible in the management of the hepatic metastases, we have used a non-operative technique of embolization to destroy the carcinoid secondaries and ameliorate symptoms. The patient tolerated this procedure well and improved dramatically, with remarkable diminution of liver size and the disappearance of all carcinoid symptoms. Destruction of hepatic secondaries without recourse to surgery has obvious advantages in severely ill patients. Careful attention should, however, be paid to the large quantities of pharmacologically active compounds released from the liver by the procedure.

Norepinephrine-producing tumors of bilateral breasts: a case report

There was a tumor in the left breast which was suspected to be carcinoid tumor at excisional biopsy. Autopsy revealed the same tumor in the right nipple. In the cells of the bilateral tumors a number of argylophil granules were diffusely demonstrated and the neurosecretory ones were verified electronmicroscopically. In the urine of the patient a moderate amount of norepinephrine was excreted. It was presumed that the norepinephrine might have been produced from the breasts. In the literature reviewed, the case of breast carcinoid has not been reported previously.

Carcinoid tumour of the cervix

A case of non-metastatic carcinoid tumour of the cervix is described from a patient without the carcinoid syndrome. The rarity of carcinoid tumour involving gynaecological structures other than the ovaries is discussed and a bried review of carcinoid disease presented.