Gastric mucosal masses, which are new organisms from the gastric mucosa, are most commonly gastric cancer (adenocarcinoma, squamous or adenosquamous), but a few are also gastric lymphomas from the submucosa. Very often, it is difficult to distinguish between the two. Even with pathological diagnosis, there is occasional misdiagnosis, and the most common misdiagnosis is gastric lymphoma as gastric cancer. Gastric carcinoma: It is a malignant tumor originating from the epithelium of the gastric mucosa and has the highest incidence rate among all kinds of malignant tumors in China, with obvious geographical differences. The age of prevalence is above 50 years old, and the ratio of male to female incidence is 2:1, but in recent years, the trend of younger incidence is obvious, and young people around 20 years old can be encountered from time to time. According to the histopathology, adenocarcinoma, adenosquamous carcinoma and squamous carcinoma can be classified, and the majority of them are adenocarcinoma. Further, adenocarcinoma can be divided into papillary, ductal, hypofractionated, mucinous, and indolent cell carcinomas. According to the degree of differentiation of cancer cells, it can be divided into highly differentiated, moderately differentiated and poorly differentiated. According to Lauren’s staging, it can be divided into intestinal type, mixed type and diffuse type. Gastric lymphoma (gastric lymphoma): malignant tumor derived from submucosal lymphoid tissue, is a common extra-lymph node lymphoma (non-Hodgkin’s lymphoma), second only to gastric cancer among malignant tumors of the stomach. It occurs in young and middle-aged men. The most common sites of disease are the gastric sinus and the anterior pylorus, and the lesions can be solitary or multiple. Diffuse large B lymphoma is the most common. The metastatic route is mainly lymphatic metastasis, similar to that of gastric cancer. The clinical symptoms of gastric lymphoma lack specificity, and the endoscopic manifestations are similar to those of gastric cancer. There may be fever, epigastric pain, abdominal mass and anemia, and some of them are combined with upper gastrointestinal bleeding, which are not clearly distinguishable from gastric cancer and gastric ulcer and easily misdiagnosed. The gastroscopic manifestations of gastric lymphoma are also somewhat different from those of gastric cancer: most of them are large masses and large ulcers; they often involve multiple sites and are diffusely distributed; the gastric mucosal folds are stiff and hypertrophic and do not unfold easily after gastric insufflation; some of them are widely nodule-like or granular, and the gastric wall is stiff. Gastric lymphoma is not easy to get tumor tissue because lymphoma originates from submucosal tissues, which is difficult to get due to superficial sampling under gastroscopy, and it is easier to get only after the tumor grows to a certain extent and involves mucosa. In addition, conventional staining, which mostly shows poorly differentiated cell types under microscope, is difficult to distinguish from hypodifferentiated gastric cancer. Therefore, it is easy to be misdiagnosed and requires further addition of immunohistochemistry to make a clear diagnosis through molecular markers specific to the surface of tumor cells. There are often patients who consult through various channels and respond that the preoperative pathology is gastric cancer, but the postoperative pathology is lymphoma. This problem mainly lies in the lack of detailed preoperative pathology diagnosis or the lack of additional immunohistochemistry. Recently, an outpatient visited a local hospital with gastroscopy suggesting poorly differentiated cancer, but after visiting another hospital, the doctor thought it was gastric cancer based on CT and gastroscopy, and performed radical gastric cancer surgery. This patient can actually do chemotherapy directly without surgery. Then, we will talk about the treatment of gastric lymphoma. Gastric lymphoma is essentially different from gastric cancer and the treatment plan is also different. In the past, it was thought that gastric lymphoma was mainly treated by surgery. With the in-depth research, it was found that chemotherapy for gastric lymphoma is very effective, and many patients can be cured by chemotherapy. Surgical treatment is not required. Surgical treatment has evolved from its former status as the mainstay to its current status as an adjuvant treatment. When is surgical treatment needed? It is mainly when tumor bleeding or tumor ulceration causes perforation or imminent perforation of the stomach wall, which requires surgery first and chemotherapy later; or when gastric bleeding or perforation occurs during chemotherapy, which requires surgery. Otherwise, all chemotherapy is administered first. The effect is then reviewed and evaluated after chemotherapy, and if it does not disappear completely, the surgery needs to be done retrospectively. However, the vast majority of patients whose tumors disappear after chemotherapy do not need surgical treatment.