This organ-tropic metastasis is known as the “seed and soil” theory.179 This conclusion was reached because CD146 was remarkably overexpressed in metastatic breast cancer cells.180–182 In 2019, in breast cancer cells, the S100A8/A9-CD146 axis-elicited downstream signals that produce the driving force for distant metastasis were identified. This evidence concerns the gene IGKV1D-22 and breast cancer.