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Clinical features of the carcinoid syndrome

Author
Jonathan R Strosberg, MD
Section Editors
Kenneth K Tanabe, MD
David C Whitcomb, MD, PhD
Deputy Editor
Diane MF Savarese, MD

INTRODUCTION

Carcinoid syndrome is the term applied to a constellation of symptoms mediated by various humoral factors elaborated by some well-differentiated neuroendocrine tumors (NETs) of the digestive tract and lungs, which synthesize, store, and release a variety of polypeptides, biogenic amines, and prostaglandins (table 1). Some of these tumor products are responsible for the carcinoid syndrome, but the relative contributions of each and the specificity of any for particular components of the syndrome are uncertain (table 2).

The pathophysiology and clinical manifestations of the carcinoid syndrome will be reviewed here. The diagnosis and treatment of this disorder are discussed separately. (See "Diagnosis of the carcinoid syndrome and tumor localization" and "Staging, treatment, and posttreatment surveillance of nonmetastatic, well-differentiated gastrointestinal tract neuroendocrine (carcinoid) tumors" and "Metastatic well-differentiated gastroenteropancreatic neuroendocrine tumors: Presentation, prognosis, imaging, and biochemical monitoring".)

FREQUENCY

Neuroendocrine tumors (NETs) may arise anywhere in the gastrointestinal tract, in the lungs, and occasionally, elsewhere (table 3). Carcinoid syndrome is most common in the setting of disseminated disease, particularly liver metastases, but it can occur in apparently locoregional disease. One reason may be understaging. Unappreciated hepatic metastases may be more common than previously reported [1-3], especially in small bowel primaries.

The liver inactivates bioactive products secreted into the portal circulation. This may explain why patients with gastrointestinal NETs most often develop carcinoid syndrome if they have hepatic metastases, resulting in the secretion of tumor products into the systemic circulation [4]. In the large majority of cases, carcinoid syndrome is associated with metastatic tumors originating in the midgut (jejunum, ileum, and cecum); however, the expression is variable in individual patients [5]. Less often, carcinoid syndrome is caused by a NET arising in the lung or in the distal colon or rectum (foregut and hindgut embryologic origin, respectively) [6]. Gastric and lung NETs may be associated with atypical carcinoid syndromes. (See 'Variant syndromes' below.)

Approximately 1 percent of pancreatic NETs secrete excess serotonin and other vasoactive substances that produce the carcinoid syndrome. (See "Clinical characteristics of carcinoid tumors".)

                 

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Literature review current through: Jul 2017. | This topic last updated: Jun 05, 2017.
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