RESUMO
<p><b>OBJECTIVE</b>To investigate the clinicopathological characteristics of colorectal neuroendocrine neoplasms (NENs) and the prognostic significance of the new WHO classification and staging system about gastroenteropancreatic NENs.</p><p><b>METHODS</b>The 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.</p><p><b>RESULTS</b>Forty-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).</p><p><b>CONCLUSIONS</b>Colorectal 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.</p>