Abstract Background/Aim:The relationship of cancer and stromal cells is poorly understood, including their ability to fuse or otherwise their genetic materials. Materials and Methods:Red-fluorescent protein (RFP-expressing) mouse colon 26 cancer cells were initially injected subcutaneously in green-fluorescent protein (GFP) nude mice. The resulting subcutaneous tumors were harvested and cultured. Using the Olympus FV1000 confocal microscope, the cells cultured from tumors were visualized. After 14 days culture, the cells were injected into the spleen. Results:After splenic injection, colon 26 metastases were observed in the liver, ascites, and bone marrow. RFP colon cancer cells, GFP stromal cells derived from host GFP nude mice, and recombinant yellow-fluorescent cells were observed in each organ. In addition, in the liver, areas with only GFP stromal cells were observed and assured to be a pre-metastatic niche. Conclusion:Color-coded imaging demonstrated the dynamics of colon cancer and stromal cells at different metastatic sites including the formation of recombinant cancer stromal cells. The significance of which will be evaluated in future experiments. Citation Format: Miki Nakamura, Atsushi Suetsugu, Kana Matsuura, Tomoyuki Satake, Masahito Shimizu, Shigetoyo Saji, Hisataka Moriwaki, Robert M. Hoffman. Recombinant cancer-stromal cells Identified in the metastatic tumor microenvironment By color-coded imaging [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1148.