Hepatoid Adenocarcinoma of Stomach

The goal of this clinical trial is to learn if treatment modality including Disitamab Vedotin （RC48）, Oxaliplatin，Tegafur,Gimeracil and Oteracil Porassium Capsules （SOX）and Sindillimab works to treat locally advanced hepatoid adenocarcinoma of stomach. It will also learn about the safety of this modality. The main aim it aims to achieve are: * To evaluate the perioperative efficacy of RC48 combined with sindillizumab and SOX in the treatment of locally advanced HER2-expressing hepatoid adenocarcinoma of stomach * To evaluate the safety and long-term benefits of RC48 combined with sindillizumab and SOX regimens in perioperative treatment of locally advanced HER2-expressing hepatoid adenocarcinoma of stomach Participants will: * Preoperative treatment with RC48, SOX and sindillizumab for 4 cycles * Radical surgery after 4-6 weeks of the preoperative treatment * Adjuvant treatment with RC48, Tegafur,Gimeracil and Oteracil Porassium Capsules and sindillizumab for 4 cycles

The goal of this clinical trial is to learn if treatment modality including albumin-bound paclitaxel, oxaliplatin, tegafur,gimeracil and oteracil porassium capsules (SOX) and sintilimab works to treat locally advanced HER2-negative hepatoid adenocarcinoma of stomach. It will also learn about the safety of this modality. The main aim it aims to achieve are: * To evaluate the perioperative efficacy of albumin-bound paclitaxel combined with sintilimab and SOX in the treatment of locally advanced HER2-negative hepatoid adenocarcinoma of stomach * To evaluate the safety and long-term benefits of albumin-bound paclitaxel combined with sintilimab and SOX regimens in perioperative treatment of locally advanced HER2-negative hepatoid adenocarcinoma of stomach Participants will: * Preoperative treatment with abumin-bound paclitaxel, SOX and sintilimab for 4 cycles * Radical surgery after 4-6 weeks of the preoperative treatment * Adjuvant treatment with albumin-bound paclitaxel, tegafur,gimeracil and oteracil porassium capsules and sintilimab for 4 cycles