Carcinoid is a rare and slow-growing tumor that originates from neuroendrocine cells in the intestinal lining.
What are the symptoms of carcinoid?
Carcinoid tumors generally produce no symptoms at all in the early stages. The majority of carcinoids are located in the rectum and are discovered incidentally at the time of a colonoscopy. Happily, rectal carcinoids tend to carry a good prognosis. In the medical community, carcinoid is best known for causing carcinoid syndrome, which is a constellation of symptoms including facial flushing (redness), diarrhea and wheezing depending on where the tumor is located and if it has spread, or metastasized, to the liver. In the case of intestinal carcinoid, if the tumor is located in the mid-gut (appendix or ileum) it may produce certain chemicals, such as serotonin. Unlike carcinoid tumors located in the small intestine, rectal carcinoids almost never secrete bioactive products.
How is rectal carcinoid diagnosed?
The majority of carcinoid tumors are discovered incidentally at the time of colonoscopy, before they produce symptoms or have spread to other organs.
How is rectal carcinoid treated?
Approximately 80% of all lesions are <1cm, without evidence of microinvasion of local lymph node spread at the time of diagnosis and therefore carry a 92% 5-year survival rate. Because they are typically located between 4 and 13 cm from the anus, many of these lesions have traditionally been amenable to trans-anal excision. Lesions within the upper rectum can also be effectively removed with snare cautery. More recently, TAMIS (Trans-Anal Minimally Invasive Surgery) has become the most effective operative technique for handling small rectal carcinoid tumors.
In 10% of rectal carcinoids, the lesions are >2 cm in size, have evidence of muscular invasion, or lymph node metastasis. For these patients, often radical surgery such as low anterior resection is typically recommended.
The remaining 10% of patients require more tailored recommendations; for lesions between 1 and 2 cm of size, an 11% risk of lymph node metastasis is predicted. For these patients in particular, additional studies, such as endo-rectal ultrasound can assist in determining likelihood of lymph node disease or extension of the carcinoid into the muscularis propria. This information is taken into consideration along with the general health of the patient and risk to the sphincters/need for a colostomy into the optimal management for the patient.
Lastly, the question of incomplete excision of a carcinoid at the time of endoscopy is a difficult one. Ideally an accurate assessment of the size of the lesion is available. A repeat endoscopy with a biopsy of the base to determine the presence of residual disease should be performed. In addition, the lesion may need to be marked before the biopsy site has healed so it can be found again. Endo-rectal ultrasound may also be of value in identifying residual disease and depth of penetration. If there is no residual disease, then the carcinoid can be considered reliably treated. If there is residual disease present, in the absence of negative prognosic factors (lymph node metastasis or invasion into the muscularis) a transanal local excision or TAMIS (TransAnal Minimally Invasive Surgery) excision of the site will suffice.