BACKGROUND OF STUDY: Adenocarcinoma cancer is the most common cancer in the world and the gastric happens rare however gastric neuroendocrine carcinoma is one of the leading causes of cancer death in the world and its pathogenesis and pathology diagnosis haven’t been not studied well. Our study is based on it. AIMS: 1.To determine by age and sex the 70 adenocarcinoma cases which diagnosed by endoscope at the National Cancer Center of Mongolia in 2013-2016 and to diagnose histology method of WHO. 2. To study the gastric cancer in pathology department by immunohistochemistry. MATERIAL AND METHODOLOGY: We worked on 70 patients with gastric cancer in 4th department at the National Cancer Center of Mongolia from 2013 until 2016. RESULT OF STUDY: We determined 70 patients with gastric cancer and of the 70 patients which diagnosed by pathology and immunohistochemistry 35 cases were 50.0% (Adenocarcinoma), 15 cases were 21.4% (gastric neuroendocrinecarcinoma), 2 cases were 2.9% (GIST-gastrointestinalstromal tumor), and 18 cases 25.7% (dysplasia). By sex of the 70 patients 39 cases 56% were males, 31 cases 44% were females and by age 17 cases 24.29% were 51-60 years old, 24 cases 34.29% were 61-70 years old. This results is shown the early 40 years old people has the great risk of this cancer. CONCLUSION: In our study 35 CD56 specific tissues were diagnosed by Ki67 markers and of them 15 cases were gastric neuroendocrine carcinoma and 18 cases were dysplasia determined.