A 31-year-old man with abdominal pain and a rectal nodule
HOW SHOULD THIS PATIENT BE MANAGED?
3. What is the appropriate management of rectal carcinoid in this patient?
- Since the nodule is 1.0 cm or smaller, watchful waiting is acceptable
- Since the nodule is 1.0 cm or smaller, local excision is appropriate, and no follow-up is required
- Because all carcinoid tumors are potentially malignant, radical resection (eg, abdominal perineal resection) is appropriate
- Because all carcinoid tumors are potentially malignant, radical resection with chemotherapy with 5-fluorouracil (Adrucil) and doxorubicin (Adriamycin) is required
Since the nodule is 1.0 cm or smaller, local excision is appropriate, and no follow-up will be required. Rectal carcinoid tumors generally have a favorable prognosis, with a 5-year survival rate of 87.5%.10
PROGNOSIS DEPENDS ON TUMOR SIZE, OTHER FACTORS
Many studies have examined risk factors contributing to poor prognosis, and this is an area of active study. Early research categorized rectal carcinoid risk in terms of tumor diameter, and this is still widely used to guide management. As early as 1959, Hanley et al5 recognized that tumors that were likely to metastasize were often larger than 1 cm, had infiltrated the muscularis, or were ulcerated. Today, it is understood that only 3% to 10% of rectal carcinoids smaller than 1 cm metastasize, whereas 17% to 42% of those 1 to 2 cm and 60% to 80% of those larger than 2 cm do.2,8,12,13
However, size is not the only consideration. Wang et al12 showed that muscular invasion is an independent risk factor for survival, and that tumor diameter is a significant predictor of invasion and metastasis. Similarly, a metaanalysis by Mani et al13 recognized tumor size and muscularis invasion as the most important predictors of malignancy in these neoplasms.
To aid in predicting prognosis, staging systems have been developed from institutional or national registries. Landry et al14 developed a TNM (tumor, node, metastasis) staging system for rectal carcinoids, in which the T value was based on tumor size and degree of invasion. A group at Memorial-Sloan Kettering Cancer Center15 developed a system for risk stratification of carcinoid of the rectum that is based on tumor size, muscularis invasion, lymphovascular invasion, and the mitotic rate.
TREATMENT IS BY EXCISION
Despite these new prognostic systems, there is no new guidance on therapeutic management. Surgical therapy is still largely guided by tumor size.
Lesions smaller than 1 cm are resected endoscopically or by another local transanal technique.2,3,15,16 Standard endoscopic mucosal resection is performed, and recent studies have suggested that endoscopic submucosal dissection is as effective17 or even preferred, because it resects to the deeper submucosa (as the name suggests).18 This en bloc technique may be appropriate for lesions with evidence of local invasion.18 Other situations may call for deeper resection, such as transanal resection for higher lesions and full-thickness mucosal-muscularis resection.
Tumors 1 to 2 cm are currently evaluated for other factors such as ulceration and umbilication, which influence the choice of local vs radical resection. Otherwise, there is little guidance for tumors of 1 to 2 cm.
Tumors larger than 2 cm have a high risk of muscularis invasion and metastasis, and hence they are resected with wide margins and imaging is then used to evaluate for metastasis.8,19 In cases of metastasis, local resection is often palliative, providing local symptom relief.19
AN INCIDENTALLY DISCOVERED CASE; PATIENT LOST TO FOLLOW-UP
Our patient’s case is typical of rectal carcinoid in that it was discovered incidentally during colonoscopy. His clinical presentation was likely unrelated to his carcinoid tumor, and he improved without specific treatment. His symptoms resolved within 24 hours with supportive treatment and he was discharged.
Pathologic confirmation of carcinoid tumor occurred after his discharge. Despite persistent attempts to contact the patient, he never returned for a follow-up appointment.
TAKE-HOME POINTS
- Carcinoid tumors are rare neoplasms of neuroendocrine origin.
- Rectal carcinoids are the third most common carcinoid of the gastrointestinal tract.
- Most rectal carcinoids are asymptomatic.
- Diagnosis is most often incidental and histologic.
- Treatment is by excision.
- Prognosis is favorable for smaller carcinoids and depends on size (and therefore, invasion).
