[Clinicopathological features and prognosis of rectal neuroendocrine tumor with grade 2]

Objective: To explore the clinicopathological features of rectal neuroendocrine tumor (R-NET) G2, identify prognostic factors, and summarize treatment experience. Methods: The clinical data of patients diagnosed with R-NET G2 by pathological diagnosis admitted to Cancer Hospital of the Chinese Academy of Medical Sciences from January 2003 to September 2023 were retrospectively analyzed. The Fisher's exact test and Kaplan-Meier curves were performed to analyze the association between pathological features and prognosis. Results: A total of 22 patients were enrolled in this study and 21 patients were followed up for a period of 6-98 months with a median follow-up time of 42 months. 5 patients died due to tumor progression during the follow-up period. The 1-, 3-, and 5-year cancer-specific survival (CSS) of the whole group were 100.0%, 92.9%, and 69.6%, respectively. Of the 22 patients, 20 underwent surgical treatment, of which 15 underwent postoperative adjuvant therapy; 2 underwent medical treatment for liver and bone multiple metastases. The 5-year survival rates of patients with tumours ≥2 cm in length, T2-3 stage, lymph node metastasis, and distant metastasis (57.1%, 68.8%, 66.7%, and 63.6%, respectively) were shorter than those of patients with tumours <2 cm in length, T1 stage, no lymph node metastasis, and no distant metastasis (all 100.0%, P＜0.001). In addition, patients with liver metastases had larger primary tumor diameters and higher T-stages compared with those without distant metastasis (P＜0.05). Conclusions: R-NET G2 has a high degree of malignancy compared with G1 and a high propensity for metastasis. Clinicians should formulate appropriate diagnostic and treatment strategies based on factors such as tumor size, depth of invasion, lymph node status, presence of distant metastasis, and the location and extent of distant metastasis.