These results indicate that the major 18F-FDG-accumulating cells in the A431 cell-derived tumor were hypoxic human S100A4-positive cells derived from the inoculated cancer cells and not vimentin-positive CAFs, including resident fibroblasts, bone marrow cells, adipocytes, endothelial cells, and epithelial cells. This evidence concerns the gene S100A4 and neoplasm.