e15527 Background: The primary tumor and associated but distinct from it premetastatic niches include a number of important participants: immune cells, stromal cells, extracellular matrix and associated effectors, in particular hormone receptors. Cross-interaction between these components is key to tumor progression. The greater omentum and peritoneum are pre-metastatic niches for gastric cancer. The purpose of the study was to analyze levels of steroid hormone receptors in tissues of gastric cancer (GC) and its pre-metastatic niches: the peritoneum (P) and omentum (O). Methods: The main group included 21 patients with metastatic GC T3-4аN0-3M1; the comparison group – 24 patients with non-metastatic GC T3-4аN0-3M0. Tissues of tumors, intact gastric tissues, omentum and peritoneum tissues were studied. The control group included 17 non-cancer patients; omental and peritoneal tissues were studied. Levels of receptors of estrogens (RE-α, RE-β), androgens (RA) and progesterone (RP4) were measured by ELISA. Results: Levels of RE-α in tissue of GC T3-4аN0-3M1 were decreased by 1.7 times (P˂0.05) compared to controls, while in T3-4аN0-3M0 they were increased by 1.2 times (P˂0.05). RE-β and RА did not change in both cases. RР4 in T3-4аN0-3M1 was similar to control levels, and in T3-4аN0-3M0 – was increased by 3.5 times. Levels of RE-α and β, RА and RР4 in O and P in T3-4аN0-3M1 were similar to control levels, and in T3-4аN0-3M0 they were higher: RE-α - by 3.9 and 2.4 times, RE-β – by 2.5 and 1.5 times (P˂0.05), RР4 – by 2.2 and 1.5 times (P˂0.05). RA in O and P in T3-4аN0-3M0 was similar to control levels. Conclusions: Elevated levels of RE-α., RE-β and RR4 in peritoneal and omental tissues can be considered a factor associated with some characteristics of GC metastasis, and protective one at the same time. Obviously, levels of RE-α and RР in O and P correlate with the levels in tissues of GC T3-4аN0-3M0. However, this statement is disputable and requires further confirmation.