Clinicopathological characteristics and prognostic analysis of gastric neuroendocrine carcinoma: A comparative study with gastric adenocarcinoma

Objective Gastric neuroendocrine carcinoma (G-NEC) is a rare and highly aggressive malignancy characterized by a dismal prognosis. Due to its low incidence, standardized treatment strategies for locoregional disease have not been firmly established. This study aimed to clarify the distinct clinicopathological features and prognostic factors of G-NEC by comparing them with those of gastric adenocarcinoma. Methods We retrospectively reviewed the medical records of 1,014 patients who underwent gastrectomy for gastric cancer at Kochi Medical School between January 2010 and December 2025. Patients were divided into two groups: the G-NEC group (n = 24) and the adenocarcinoma group (n = 990). Clinicopathological parameters including age, sex, tumor location, depth of invasion (T stage), and vascular involvement were compared, and long-term survival outcomes were evaluated. Results G-NEC accounted for 2.4% of the total cohort. The G-NEC group exhibited a significant male predominance compared to the adenocarcinoma group (87.5% vs. 64.7%, P  = 0.036). Regarding tumor progression, G-NEC patients presented with significantly deeper tumor invasion (T4: 62.5% vs. 27.9%, P  = 0.006) and a markedly higher rate of venous infiltration (75.0% vs. 37.1%, P  < 0.001). No significant differences were observed in tumor size, location, or lymphatic infiltration. Survival analysis demonstrated that patients with G-NEC had significantly poorer overall and recurrence-free survival compared to those with adenocarcinoma, primarily due to early systemic recurrence and hematogenous metastasis. Conclusion G-NEC is a biologically aggressive entity characterized by deep local invasion and frequent vascular involvement. Given the high risk of early systemic failure, a multidisciplinary approach combining radical surgery with potent systemic chemotherapy is essential for improving clinical outcomes.