intestinal carcinoid tumor
Within the gastrointestinal tract, nearly 45% of carcinoids arise in the small intestine, making this the most common location for carcinoid tumors.
Likewise, carcinoid tumors account for the highest percentage of small bowel tumors, representing approximately one third of all small intestinal neoplasms.
Presumed to arise from the intraepithelial endocrine cells disseminated throughout the intestine, small bowel carcinoids most commonly occur in the distal ileum within 60 cm of the ileocecal valve; moreover, the incidence of these tumors increases with proximity to the cecum.
These tumors commonly present in the sixth or seventh decade of life with symptoms of abdominal pain or small bowel obstruction (SBO).
SBO has been recognized as an increasing feature of this tumor because of anecdotal evidence of tumor infiltration into the mesentery, provoking an intense fibrotic reaction that results in kinking of the bowel segments with resultant intestinal ischemia.
Small bowel carcinoids are frequently multiple, exhibiting multicentricity in up to 30% of patients, and often display metastases to the lymph nodes (39%) or the liver (31%).
Development of typical carcinoid syndrome is rare, manifesting in approximately 5%–7% of patients; however, younger patients are more likely to develop carcinoid syndrome and display a worse prognosis.
The overall 5-year survival rates are estimated at 65% and 35% for locoregional and distant disease, respectively.
Carcinoid tumor of the small intestine are fairly well circumscribed but not encapsulated, white or pale yellow tan, and very firm because of a marked desmoplastic reaction.
Carcinoid tumors of the small intestine are frequently associated with mechanical obstruction of the intestine as a result of extensive mesenteric fibrosis
Variants
multiple intestinal carcinoid tumors (#15043324#)
See also
carcinoid tumors
- digestive carcinoid tumors
Treatment
Small bowel carcinoids frequently present with nodal and mesenteric metastases, the latter of which may induce an intense local desmoplastic reaction capable of producing SBO secondary to fibrosis and ischemia.
The surgical management of patients with small bowel carcinoids depends largely on the tumor size, location, and metastatic spread.
For tumors <1 cm in greatest dimension without evidence of regional lymph node metastases, segmental resection alone with close postoperative surveillance is adequate.
A more aggressive surgical approach is necessary for patients with tumors >1 cm, those with locoregional lymph node metastases, and those with mesenteric spread.
In these patients, the preferred treatment is a small bowel resection with the associated mesentery and mesenteric lymph nodes, the latter of which has been shown to be associated with longer disease-free survival.
Importantly, in the presence of aggressive disease, the primary small bowel tumor is often small when compared with the associated regional lymphadenopathy or distant metastases; however, even in the presence of distant disease spread, there is evidence to suggest that outcomes are better if the primary tumor is resected.