[Study of FGFR2 status in gastric cancer by immunohistochemistry and fluorescent in situ hybridization].

Background: Assessment of FGFR2 status in gastric cancer is an important task, without clarification of which it is impossible to identify a cohort of patients in whom the best response to treatment with anti-FGFR2 drugs could be obtained.

Objective: To conduct a comparative analysis of the expression and amplification of the gene in gastric cancer in primary tumors and metastases in the lymph nodes.

Material And Methods: FGFR2 status was studied in 61 patients with stage III gastric adenocarcinoma using an immunohistochemical method (Abcam clone EPR24075-418, R&D clone 98706, Santa Cruz clone C-8, Abcam clone 1G3) and FISH.

Results: The antibody Abcam clone EPR24075-418 was found satisfactory for the immunohistochemical study of FGFR2. FGFR2 expression was detected in 26 (43%) cases, amplification in 5 (8%) cases. Amplification of in 4 cases out of 5 was accompanied by the expression of 3+, in 1 case - 2+. Discordance between FGFR2 expression in primary tumor and lymph node metastases was revealed in 13 (21%) cases.

Conclusion: Clone EPR24075-418 showed the best result in assessing the expression of FGFR2: the correlation with FISH results in reaction 3+ was 100%. Due to the high heterogeneity of FGFR2 expression, it is recommended to either examine the material of the primary tumor and metastasis, or evaluate a large volume of the primary tumor.