Brief Summary
Lymph node metastasis (LNM) is a key factor influencing treatment decisions and prognosis in patients with gastric cancer. Lymphatic invasion (LI) is an important pathological predictor of LNM and a core component of the eCURA risk scoring system after endoscopic submucosal dissection (ESD) for early gastric cancer. However, whether LI has the same predictive value for LNM across different mismatch repair (MMR) statuses remains unclear. Compared with proficient mismatch repair (pMMR) gastric cancer, deficient mismatch repair (dMMR) gastric cancer has distinct molecular pathological features and an immune-enriched tumor microenvironment. In early gastric cancer, if LI is associated with a lower LNM risk in dMMR tumors than in pMMR tumors, existing LI-based eCURA risk assessment may overestimate LNM risk in patients with dMMR early gastric cancer and consequently affect decisions regarding additional surgery after ESD. Therefore, this study aims to systematically evaluate the impact of MMR status on the association between LI and LNM using upfront-surgery and post-ESD additional-surgery cohorts from our center, and to explore the potential clinical value of MMR status in refining eCURA-based risk stratification for early gastric cancer.
Upfront surgery cohort
Patients who underwent radical surgery for gastric cancer at Zhongshan Hospital, Fudan University.
Patients who did not receive neoadjuvant chemotherapy, radiotherapy, immunotherapy, or other antitumor treatments that may affect the pathological assessment of the primary tumor or lymph node metastasis before surgery.
Patients with pathologically confirmed gastric adenocarcinoma or gastroesophageal junction adenocarcinoma after surgery, including Siewert type II and III tumors only.
Upfront surgery cohort
Patients with other pathological types, such as gastric squamous cell carcinoma or neuroendocrine carcinoma.
Patients who received neoadjuvant treatment before surgery, including chemotherapy, radiotherapy, immunotherapy, targeted therapy, or other systemic antitumor treatments.
Patients with missing postoperative pathological information, resulting in inability to determine lymphatic invasion or regional lymph node metastasis status.
Patients with pathologically confirmed gastric adenocarcinoma or gastroesophageal junction adenocarcinoma treated at Zhongshan Hospital, Fudan University. The study population includes two retrospective cohorts: patients who underwent upfront radical surgery between January 2018 and April 2026, and patients who underwent endoscopic submucosal dissection (ESD) between January 2021 and March 2026 with available mismatch repair (MMR) status. Patients are classified according to MMR status as deficient mismatch repair (dMMR) or proficient mismatch repair (pMMR).
Cohort
Retrospective
Mismatch repair (MMR) status
Other interventionMismatch repair (MMR) status was assessed as part of routine pathological evaluation. Patients were classified as deficient mismatch repair (dMMR) or proficient mismatch repair (pMMR) according to immunohistochemical expression of MLH1, PMS2, MSH2, and MSH6.
Lymphatic invasion status
Other interventionLymphatic invasion status was determined from routine pathological reports and classified as LI-positive or LI-negative.
Lymph Node Metastasis Rate Among LI-Positive Gastric Cancer Patients
LI positivity is defined as lymphatic invasion explicitly documented in the pathological report or tumor emboli within lymphatic vessels confirmed by D2-40 immunohistochemistry. LNM is defined as regional lymph node metastasis confirmed by postoperative pathological examination. The LNM rate among LI-positive patients is calculated as the number of patients with LNM divided by the total number of LI-positive patients in the corresponding group.
LI Positivity Rate According to MMR Status
This outcome evaluates differences in LI positivity rate between patients with dMMR and pMMR gastric cancer. LI positivity rate is calculated as the number of LI-positive patients divided by the total number of patients in each MMR group.
Overall LNM Rate According to MMR Status
This outcome evaluates differences in overall LNM rate between patients with dMMR and pMMR gastric cancer. Overall LNM rate is calculated as the number of patients with pathologically confirmed LNM divided by the total number of patients in each MMR group.
eCURA Risk Stratification and LI Contribution in the Gastric Cancer ESD Cohort
This outcome evaluates differences in eCURA classification, eCURA risk score distribution, and the contribution of LI to the risk score between dMMR and pMMR patients in the gastric cancer ESD cohort. LI contribution is assessed based on its role in eCURA-C2 classification and/or its component score contribution within the eCURA risk scoring system.
LNM Rate Among LI-Positive Patients in the cohort undergoing additional gastrectomy after ESD
This outcome evaluates differences in LNM risk between LI-positive dMMR and pMMR patients with early gastric cancer who underwent additional surgery after ESD. LNM is defined as regional lymph node metastasis confirmed by pathological examination of the additional surgical specimen. LNM rate is calculated as the number of patients with LNM divided by the total number of LI-positive patients in each MMR group.
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