Relevance: Gastric cancer continues to lead the cancer incidence structure. One of the directions of a comprehensive plan to reduce the
 incidence of malignant neoplasms is the development a highly efficient early diagnostics based on the relationship between the expression of
 the cell proliferation marker Ki-67 in gastric cancer with age, sex, stage of the disease and the degree of tumor differentiation according to
 immunohistochemical analysis.
 The study aimed to study the relationship between the expression of the Ki-67 marker in gastric cancer and age, sex, stage of the disease,
 and the degree of tumor differentiation.
 Methods: The research design is a comparative descriptive study. For the study, surgical material was used from 109 patients with gastric
 cancer stages 0-IIIC, obtained during gastric cancer operations from the pathology department of the West Kazakhstan Marat Ospanov
 Medical University (WKMOMU) Medical Center from 2021 to 2022. Histological and immunohistochemical studies were conducted at the
 morphological laboratory of the Department of Histology of WKMOMU. The obtained data was statistically processed.
 Results: The present study showed a significant statistical correlation between the Ki-67 level and the histopathological grade of gastric
 cancer (p=0.039).
 The indicators such as ‘pTNM stage’ (p=0.894), ‘Age’ (p=0.664), ‘Sex (F – 1, M – 2)’ (p=0.928), and ‘Tumor localization (cardiac – 1, body – 2,
 antral and pyloric – 3)’ (p=0.866) did not statistically significantly correlated with the Ki-67 expression level.
 Conclusions: The relationship between Ki-67 expression and histopathological grade (p=0.039) in gastric cancer helps identify patients
 with aggressive tumors that require adjuvant therapy.