This study aims to examine the predictive value of metastatic gastric mesenteries, which contains metastatic lymph node, in 6 gastric mesenteries; and importantly, to further evaluate the relationship between the number of metastatic gastric mesenteries and prognosis in the gastric cancer patients who received D2+complete mesogastric excision (CME).

Prior to 2010, the gastric cancer nodal staging systems primarily consisted of two approaches: the UICC/AJCC classification (by the International Union Against Cancer/American Joint Committee on Cancer), which was based principally on the number of metastatic lymph nodes; and the JGCA system (by the Japanese Gastric Cancer Association), which focused on the anatomical location of metastatic lymph nodes. However, a landmark unification occurred in the 14th edition of the Japanese Classification of Gastric Carcinoma (2010), where the anatomically based nodal staging was abolished in favor of a metastasis-counting method. This harmonization with the UICC/AJCC system established a globally authoritative standard for evaluating therapeutic outcomes in gastric cancer, representing a milestone advancement in clinical research.

The current staging standard for gastric cancer follows the 8th edition TNM classification system (effective in 2017) jointly established by the UICC and AJCC, which primarily evaluates tumor invasion depth (T), lymph node metastasis extent (N), and distant metastasis status (M). By integrating these three parameters, gastric cancer is classified into stages 0 through IV to guide treatment decisions and prognostic assessment. The gastric mesentery contains vascular, adipose, neural, and lymphoid tissues and can be anatomically divided into the left gastric mesentery, right gastric mesentery, left gastroepiploic mesentery, right gastroepiploic mesentery, posterior gastric mesentery, and short gastric mesentery. Although the anatomical location of metastatic lymph nodes is no longer included in the current gastric cancer staging system, our institutional research has demonstrated that, among patients with the same N-stage, those with a greater number of metastatic gastric mesenteries exhibit worse prognosis, indicating that the anatomical distribution of metastatic lymph nodes remains clinically significant for gastric cancer outcomes. This study proposes to examine lymph nodes in individual gastric mesenteries in the clinical specimens in the patients with gastric cancer who received D2+CME. Compared to the lymph node grouping described in the 15th edition of the Japanese Gastric Cancer Association's "Japanese Classification of Gastric Carcinoma" (2017), 16 groups of lymph nodes or more need to be separately examined, implying that this work is labor consuming. In contrast, in our system, the lymph nodes in only maximum to 6 gastric mesenteries need to be respectively examined, which will greatly decrease labor. And importantly, our system integrates the information of anatomical location of metastatic lymph nodes. By examining metastatic lymph nodes in individual gastric mesenteries, we aim to further investigate the relationship between the location and/or the number of metastatic gastric mesenteries and prognosis in the patients with gastric cancer.

Inclusion Criteria:

1. Aged older than 18 years and younger than 85 years
2. Primary gastric adenocarcinoma confirmed by preoperative pathology result
3. cT2-4aN0-3M0 at preoperative evaluation according to the American Joint 8 Committee on Cancer (AJCC) Cancer Staging Manual 8th Edition
4. Patients who received gastrectomy with D2 lymphadenectomy plus complete mesogastric excision
5. American Society of Anesthesiologists (ASA) class I, II, or III
6. Written informed consent

Exclusion Criteria:

1. Negative preoperative biopsy
2. Too late tumour stage or metastasis (cT4b/M1)
3. BMI>30 kg/m2
4. Total gastrectomy or proximal gastrectomy
5. previous neoadjuvant chemotherapy or radiotherapy
6. Previous upper abdominal surgery
7. Combined with other malignant diseases
8. Reject operation

Patients who met the above inclusion and exclusion criteria