To investigate the clinicopathological characteristics and their relationship with prognosis of colorectal neuroendocrine neoplasms (NEN) .

Medical records of 329 patients with colorectal NEN between June 2001 and July 2016 from 6 large scale centers in China were reviewed to investigate the clinicopathological characteristics and their relationship with prognosis of colorectal NEN.

(1) Colonic NEN: A total of 41 patients with colonic NEN were enrolled from The First Affiliated Hospital of Sun Yat-sen University (n= 11) , Sun Yat-sen University Cancer Center (n= 15) , Guangdong General Hospital (n= 10) , Sun Yet-san Memorial Hospital of Sun Yat-sen University (n= 3) and Fudan University Shanghai Cancer Center (n= 2) . 41 cases, including 20 males and 21 females with a mean age of (58.7 ± 4.7) years. Twenty-three colonic NEN originated in hindgut (23/41, 56.1%) , and 20 patients were stage Ⅳ (20/41, 48.8%) . Nine cases (22.0%) were neuroendocrine tumor (NET) , 25 (61.0%) were neuroendocrine carcinoma (NEC) and 7 (17.1%) were mixed adenoendocrine carcinoma (MANEC) . Six cases (14.6%) were G1 grade, 3 (7.3%) were G2 grade and 32 (78.1%) were G3 grade. Ulcerative or cauliflower-like tumors were the most common appearance under endoscopy (both 9/41, 22.0%) . Thirty-three patients (80.5%) underwent surgery. During follow-up, 19 cases died and the 3-year survival rate was 46.1%. Multivariate analysis revealed that stage Ⅳ was an independent risk factor of poor prognosis (HR= 3.871, 95%CI: 1.342 to 11.167, P= 0.012) in colonic NEN patients. (2) Rectal NEN: A total of 288 patients with rectal NEN were enrolled from The First Affiliated Hospital of Sun Yat-sen University (n= 130) , Nanfang Hospital of Southern Medical University (n= 115) and Fudan University Shanghai Cancer Center (n= 43) . Two hundred and eighty-eight cases, including 181 males and 107 females with a mean age of (47.7 ± 1.5) years. One hundred and ninety-seven patients were stage Ⅰ (197/288, 68.4%) . Of 288 rectal NEN cases, 267 (92.7%) were NET, 20 (7.0%) were NEC and 1 (0.3%) was MANEC; 214 (74.3%) were G1 grade, 53 (18.4%) were G2 grade and 21 (7.3%) were G3 grade. Submucosal tumor was the most common appearance under endoscopy (164/288, 56.9%) . Most of the rectal NET G1/G2 tumors were submucosal (146/214, 68.2%; 18/53, 34.0% respectively) while most of G3 tumors were cauliflower-like (14/21, 66.7%) . A total of 175 patients (60.8%) underwent endoscopic therapy, while 96 patients (33.3%) underwent surgery. During follow-up, 12 cases died and 3-year survival rate was 94.0%. Multivariate analysis revealed that poor differentiation as NEC or MANEC (HR= 8.919, 95% CI: 1.911 to 41.637, P= 0.005) and stage Ⅲ to Ⅳ (HR= 10.304, 95% CI: 1.772 to 59.916, P= 0.009) were independent risk factors of poor prognosis in rectal NEN patients.

The clinicopathological manifestations of rectal NEN and colonic NEN are quite different. Rectal NEN are more common with better differentiation and has better prognosis than colonic NEN.

Colonic neuroendocrine neoplasms; Rectal neuroendocrine neoplasms; Clinical manifestations; Endoscopic features; Prognosis