The Japanese Classification of Gastric Carcinoma, 3rd English Edition, provides a detailed framework for the clinical and pathological staging of gastric cancer. The classification uses the letters T, N, and M to describe the extent of the primary tumor, regional lymph node involvement, and distant metastasis, respectively. The clinical classification (c) is determined before surgery, while the pathological classification (p) is based on post-surgical findings. Tumor characteristics are recorded in a specific order, including location, macroscopic type, size, histological type, depth of invasion, and resection margins. The anatomical extent of the tumor is described based on the stomach's three regions (upper, middle, lower) and the esophagogastric junction (EGJ). Tumors in the EGJ area are classified as EGJ carcinomas regardless of histological type. The stomach's cross-sectional circumference is divided into four parts, and circumferential involvement is recorded as Circ. Macroscopic types are categorized as superficial or advanced, with further sub-classifications for superficial tumors. Histological classification includes the recording of different histological components in descending order of surface area. The depth of tumor invasion is recorded as T categories, with T0 indicating no tumor, T1 confined to the mucosa or submucosa, and T4 indicating invasion beyond the serosa. Lymph node metastasis is classified as N0–N3, with N3a and N3b indicating more extensive involvement. Distant metastasis is classified as M0 (no metastasis) or M1 (metastasis). The classification also includes the evaluation of resection margins, residual tumor, and response to preoperative treatment. The Japanese Gastric Cancer Association developed specific criteria for evaluating tumor response to chemotherapy and radiotherapy, including the use of RECIST guidelines. The resected specimen is described, prepared, and sectioned according to specific protocols to ensure accurate histological diagnosis. The classification is essential for treatment planning and prognosis assessment.The Japanese Classification of Gastric Carcinoma, 3rd English Edition, provides a detailed framework for the clinical and pathological staging of gastric cancer. The classification uses the letters T, N, and M to describe the extent of the primary tumor, regional lymph node involvement, and distant metastasis, respectively. The clinical classification (c) is determined before surgery, while the pathological classification (p) is based on post-surgical findings. Tumor characteristics are recorded in a specific order, including location, macroscopic type, size, histological type, depth of invasion, and resection margins. The anatomical extent of the tumor is described based on the stomach's three regions (upper, middle, lower) and the esophagogastric junction (EGJ). Tumors in the EGJ area are classified as EGJ carcinomas regardless of histological type. The stomach's cross-sectional circumference is divided into four parts, and circumferential involvement is recorded as Circ. Macroscopic types are categorized as superficial or advanced, with further sub-classifications for superficial tumors. Histological classification includes the recording of different histological components in descending order of surface area. The depth of tumor invasion is recorded as T categories, with T0 indicating no tumor, T1 confined to the mucosa or submucosa, and T4 indicating invasion beyond the serosa. Lymph node metastasis is classified as N0–N3, with N3a and N3b indicating more extensive involvement. Distant metastasis is classified as M0 (no metastasis) or M1 (metastasis). The classification also includes the evaluation of resection margins, residual tumor, and response to preoperative treatment. The Japanese Gastric Cancer Association developed specific criteria for evaluating tumor response to chemotherapy and radiotherapy, including the use of RECIST guidelines. The resected specimen is described, prepared, and sectioned according to specific protocols to ensure accurate histological diagnosis. The classification is essential for treatment planning and prognosis assessment.