Background: Extra-appendiceal colorectal neuroendocrine tumors are rare neoplasms with a variable biological behavior.
Materials and methods: The study group consisted of 15 patients with an extra-appendiceal colorectal neuroendocrine tumor who underwent surgical resection (M/F=3:12, mean age=62.9 years). Lower-grade neuroendocrine tumors and neuroendocrine carcinomas were recognized in 5 and 10 patients, respectively. Data were evaluated retrospectively with regard to clinical and pathologic characteristics and outcomes.
Results: The median age of the patients with lower-grade NETs was significantly lower than that in patients with NECs (53 yr vs. 68 yr, p=0.03). NETs G1-G2 were significantly smaller than neuroendocrine carcinomas (4.0 cm vs. 6.4 cm, p=0.02). There were no differences between lower-grade NETs and NECs with regard to tumor location, rate of nodal involvement and distant metastases. All the patients underwent open segmental resection of the colon or rectum. Complete resection was achieved in 3 of 5 patients from the lower-grade NET group, and in 5 of 10 patients in the NEC group. Overall survival was significantly better for lower-grade NETs tumors (p=0.005). The median survival was 4.8 months in the NEC group. The median survival in the lower-grade NET group was not achieved after a median follow-up of 69 months. Three-year overall survival was 100% for lower-grade NETs, and only 27% for NECs.
Conclusion: Lower-grade neuroendocrine tumors seem to exhibit comparable potential for dissemination as neuroendocrine carcinomas, but prognostic implications of metastases are distinct.
Keywords: colorectal neuroendocrine tumor; colorectal surgery; gastrointestinal neoplasms.