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Metastatic Pattern of Spread of Gastrointestinal Carcinoid  adult

Introduction: A low-grade neuroendocrine tumor of the gastrointestinal tract (2/3 of all carcinoids occur in the GI tract). It can be associated with the carcinoid syndrome (almost exclusively if it is of small bowel origin, upon metastasis to the liver). Metastases are very uncommon with appendiceal origin carcinoids but otherwise are common.

Prevalence: Very Rare Metastasis Frequency: Uncommon

Cancer. 2003 Feb 15;97(4):934-59. PMID: 12569593

Radiographics. 2007 Jan-Feb;27(1):237-57. PMID: 17235010

Oncologist. 2005 Feb;10(2):123-31. PMID: 15709214

AJR Am J Roentgenol. 2004 Mar;182(3):559-67. PMID: 14975946

J Nucl Med. 2003 Feb;44(2):184-91. PMID: 12571207

Primary Tumor:

 Characteristics Comments
Small Intestine Submucosal, Enhancing The small intestine is the most common site for GI carcinoids. The appendix used to be the most common site but is a rare site in the most recent series. The second most common site is rectum, followed by colon and stomach.

The primary tumor can be single or multiple in the small intestine. It is often overshadowed by mesenteric lymphadenopathy in size (and occasionally is not found at all). It often projects into the lumen and can cause intussusception.

Known Metastatic Locations:

SiteFrequencyCharacteristics Comments
Local Lymph Nodes CommonDesmoplastic, Fibrosing, Calcified Fibrosis (desmoplastic reaction) can cause kinking of bowel and obstruction. Often the mesenteric lymphadenopathy may be larger than the primary tumor, in the case of small intestine primaries. Around 70% of mesenteric lymph node metastases contain calcification.
radiology image: Calcified Desmoplastic Mesenteric Lymphadenopathy
Liver CommonHyperenhancing, Arterially Enhancing most common distant site. Metastases will be hyperenhancing in the arterial phase, although they may become isointense to liver on later phases.
radiology image: Arterially Enhancing Liver Metastases
Lung Parenchyma UncommonNodule
Bone UncommonBlastic, Lytic Classically, these are blastic metastases, but a recent series showed both lytic and blastic lesions (PMID: 12571207).
radiology image: Osteoblastic Metastases
Peritoneum Rare
Pancreas Rare
Skin (Cutaneous and Subcutaneous) Very Rare