From the Guidelines
For this 55-year-old gentleman with an incidentally found 8 mm rectal carcinoid tumor confined to the submucosa with low mitotic rate, I would recommend option #1: no further management. The patient has a well-differentiated neuroendocrine tumor (carcinoid) that is completely resected and has favorable features, including a size less than 1 cm and low mitotic rate, which suggests an excellent prognosis 1. According to the guidelines, for rectal tumors less than 1 cm, prognosis is excellent and no follow-up is usually required 1. Key points to consider in this case include:
- The tumor size is less than 1 cm, which is associated with a low risk of metastasis and an excellent prognosis 1.
- The tumor is confined to the submucosa and has a low mitotic rate, further supporting a favorable prognosis 1.
- The guidelines do not recommend routine follow-up for rectal carcinoid tumors less than 1 cm in size, which suggests that no further management is necessary in this case 1. Therefore, based on the current evidence and guidelines, no further management is recommended for this patient.
From the Research
Management of Rectal Carcinoid Tumor
The patient has undergone screening colonoscopy and been diagnosed with a rectal carcinoid tumor measuring 8 mm, confined to the submucosa with no evidence of mitotic rate greater than 2 per high-power field. Considering the tumor size and depth of invasion, the following management options are recommended:
- No further management: Not recommended as rectal carcinoids have malignant potential and require further evaluation to rule out lymph node metastasis 2, 3.
- Cross-sectional imaging: Recommended to evaluate for lymph node metastasis and distant metastasis 3, 4. A study found that lymph nodes 5 mm or larger in size identified on preoperative CT suggest the presence of metastasis 3.
- Rectal ultrasound: May be useful in staging rectal carcinoids, but its role is not well established in the management of these tumors 4.
- Surgical referral: Recommended if lymphatic invasion or nodal involvement is present, or if the tumor is larger than 10 mm in size 2, 3. A study found that tumor size and lymphovascular invasion are useful in predicting lymph node metastasis 3.
Staging and Evaluation
The patient's tumor size is 8 mm, which is less than 10 mm, but still requires evaluation for lymph node metastasis. A study found that rectal carcinoids with lymph node metastasis are common, and that tumor size and lymphovascular invasion are useful in predicting lymph node metastasis 3. Cross-sectional imaging, such as CT or MRI, may be useful in evaluating for lymph node metastasis and distant metastasis 3, 4.
Treatment
The treatment of rectal carcinoids depends on the tumor size, depth of invasion, and presence of lymph node metastasis. For tumors less than 10 mm in size, localized to the mucosa or submucosa, minimally invasive resection may be sufficient 5. However, if lymphatic invasion or nodal involvement is present, surgical referral is recommended 2, 3.