[Clinicopathological characteristics of rectal neuroendocrine neoplasms]

Objective: Clinicopathological characteristics of neuroendocrine neoplasms are highly heterogeneous based on variable origins.Our study aims to explore the clinical features of rectal neuroendocrine neoplasm (RNEN). Methods: Patients with histologically diagnosed rectal neuroendocrine neoplasms were retrospectively analyzed between January 2012 and December 2020. Epidemiological characteristics, clinical manifestations, complete blood count, endoscopy findings, and pathological features were recorded and analyzed. T-test was used for measurement data analysis, Chi-square test was performed for classification data analysis, and Binary logistic regression was applied for analyzing risk factors of metastasis. Results: Among 172 patients, the male to female ratio was 107 to 65 with an average age of (52±12) years (16-77 years). Altered bowel habit was the most common initial symptom (58/172, 33.7%), followed by abdominal pain (36/172, 20.9%) and loss of body weight (27/172, 15.7%). One hundred and sixty-one cases were neuroendocrine tumors, 9 were neuroendocrine carcinomas and 2 were mixed neuroendocrine-non-neuroendocrine neoplasms. Most endoscopic presentations were polypoid lesions (147/172, 85.5%), mainly limited to mucosa (48/172, 27.9%) and submucosa (96/172, 55.8%). Twenty-nine patients developed lymph node invasion or distant metastasis at diagnosis. There were statistical difference of neutrophil-to-lymphocyte ratios (NLR) among groups with different tumor size (<10 mm vs. 10-20 mm vs.>20 mm, mean NLR 1.79±0.55 vs. 2.27±1.23 vs. 2.95±0.66, P<0.01. Compared with non-metastatic group, the metastatic group presented higher NLR(2.61±0.81 vs. 1.89±0.80, P<0.01). Tumor size (<10 mm vs. 10-20 mm vs.>20 mm, OR 1.00 vs. 2.10 vs. 5.25×10⁹, P =0.001), invasion to bowel wall (mucosa vs. submucosa vs. muscularis vs. serosa invasion,OR 1.00 vs. 3.26 vs. 14.11 vs. 39.42, P=0.008), and NLR (NLR<2.25 vs. NLR≥2.25, OR 1.00 vs. 5.19, P =0.024) were risk factors for metastasis. Conclusion: Metastasis of RNEN is related with tumor size, degree of bowel invasion and NLR. High NLR is a poor prognostic factor of RNEN.