TGFB1 and neoplasm: Starting from these considerations, we would like to verify and point out what has just been affirmed: analyzing the different players in the metastatic process, we will consider, in particular, the tumor microenvironment (TME), the extracellular matrix (ECM), TGF-β, the epithelial–mesenchymal transition (EMT), cancer-associated fibroblasts (CAFs), and the metastatic niche.