Metastatic Pattern of Spread of Gastrointestinal Carcinoid
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
References:
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:
| Site | Frequency | Characteristics | Comments |
| Local Lymph Nodes | Common | Desmoplastic, 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.
|
| Liver | Common | Hyperenhancing, Arterially Enhancing | most common distant site. Metastases will be hyperenhancing in the arterial phase, although they may become isointense to liver on later phases.
|
| Lung Parenchyma | Uncommon | Nodule | |
| Bone | Uncommon | Blastic, Lytic | Classically, these are blastic metastases, but a recent series showed both lytic and blastic lesions (PMID: 12571207).
|
| Peritoneum | Rare | ||
| Pancreas | Rare | ||
| Skin (Cutaneous and Subcutaneous) | Very Rare |