title: Clinical characteristics of colorectal carcinoid tumors.
abstract: OBJECTIVE
  The carcinoid tumor was recently categorized as a malignant disease due to its possibility of metastasis. This study was aimed to investigate the clinical characteristics and the metastatic rate of colorectal carcinoid tumors.
  
  
  METHODS
  Charts were reviewed for 502 patients diagnosed with and treated for colorectal carcinoid tumors between January 2006 and December 2009. The location, size, depth and metastatic status of the tumors were collected.
  
  
  RESULTS
  Including 24 synchronous tumors from 12 patients, 514 carcinoid tumors were removed. Most of them were found in the rectum (97.3%). The male-to-female ratio was 1.38 to 1, and mean age was 50.2 ± 11.4 years. The mean tumor size was 5.8 ± 3.6 mm. Less than 10-mm-sized tumors had a 1.95% lymph node metastatic rate; tumors with sizes from 10 mm to 20 mm and larger than 20 mm had 23.5% and 50% lymph node metastatic rates, respectively. Two cases had distant metastasis; one with a 22-mm-sized tumor metastasized to the liver, and the other with a 20-mm-sized tumor metastasized to the peritoneum. Among 414 patients who completed metastatic studies, 93.8% were classified as stage I, 0.9% as stage II, 4.8% as stage III and 0.5% as stage IV.
  
  
  CONCLUSIONS
  Colorectal carcinoid tumors smaller than 10 mm have a low rate of lymph node metastasis, but those sized 10 mm or larger incur significant risk. Further investigation regarding additional risk factors should be done to develop proper treatment guidelines for these tumors.