Clinicopathological characteristics and prognosis of rectal well-differentiated neuroendocrine tumors

Background  To clarify the oncological outcome of rectal well-differentiated neuroendocrine tumors (W/D NETs), we examined the clinicopathological characteristics and prognosis of patients with this neoplasm. Materials and methods  A total of 23 patients who underwent surgical treatment with lymph node dissection for rectal W/D NETs between 1973 and 2007 were reviewed. Results  Median tumor size measured preoperatively was 13 mm (range, 4–25 mm), and the median number of dissected lymph nodes was 16 (range, 1–46). The incidence of lymph node metastasis was 61% (14 of 23 cases). The smallest W/D NETs with lymph node metastasis was 10 mm in diameter. All the patients without lymph node metastasis survived without recurrence. Among 11 patients who had only regional lymph node metastasis, only one developed liver metastasis and died 13 months after initial surgery. Among three patients with lateral pelvic lymph node metastasis, two survived more than 5 years, although two had liver metastasis. Conclusions  Because the incidence of lymph node metastasis is very high in patients with rectal W/D NETs greater than 10 mm in diameter, radical surgery is required. In this series, the outcome of rectal W/D NETs patients with lateral pelvic lymph node metastasis was better than expected.