OBJECTIVETo investigate the clinicopathological characteristics of colorectal neuroendocrine neoplasms (NENs) and the prognostic significance of the new WHO classification and staging system about gastroenteropancreatic NENs.

METHODSThe clinical and pathological records were reviewed in 73 patients with colorectal NENs (carcinoids). All slides were retrieved and reviewed, immunohistochemical staining (EnVision method) was performed and follow-up information retrieved.

RESULTSForty-one men and thirty-two women were included with a median age of 53 years (19 - 79 years). The location of the primary tumors in 65 patients was within 10 cm from the anorectal line. In 45 cases, the tumor diameter was ≤ 1 cm (no metastasis occurred); in 11 cases, the tumor diameter was > 1 cm but ≤ 2 cm (two patients had metastatic tumors); in 17 cases, the tumor diameter was > 2 cm (12 patients had metastatic tumors). The metastatic rate was significantly correlated with tumor size (P = 0.000). All tumors were immunoreactivity for synaptophysin and/or chromogranin A. According to the criteria of WHO classification and staging system about gastroenteropancreatic NENs, there were 65 cases of neuroendocrine tumors, including 51 cases of grade 1 (G1), 14 cases of grade 2 (G2), 4 cases of neuroendocrine carcinoma (G3) and 4 cases of mixed adenoneuroendocrine carcinoma. Following-up data showed that of the 34 patients with G1 tumor, there were no tumor-related death, but two patients showed metastases, and the remaining patients were disease free for 6 to 179 months. Of the 12 patients with G2 tumors, five developed metastasis, there were two tumor-related deaths, and the nine surviving patients were alive for 17 to 118 months. Of the four G3 patients, all developed metastasis and there were three tumor-related deaths. Of the four mixed adenoneuroendocrine carcinoma there were two tumor-related deaths. The difference of metastatic rate, tumor-related mortality, and overall survival among different grading groups in this series was statistically significant (P = 0.000).

CONCLUSIONSColorectal neuroendocrine neoplasm is a group of tumors with distinct prognostic difference, and most of these tumors show an indolent clinical behavior. There is a good correlation between the new WHO classification and staging system of gastroenteropancreatic NENs and their clinical behaviors.