This process links upstream cell surface receptors such as EGFR, fibroblast growth factor receptor (FGFR) and human epidermal growth factor receptors 2–4 (HER2–4/ERBB2–4) to downstream pathways (e.g., rat fibrosarcoma/mitogen-activated protein kinase kinase/extracellular regulated kinase (RAF/MEK/ERK), phosphoinositide 3-kinase/protein kinase B/mechanistic target of rapamycin kinase (PI3K/AKT/mTOR) and Ral guanine nucleotide dissociation stimulator (RALGDS-RA)) promoting cell proliferation, differentiation or cell death [11,12,13,14,15,16] (Figure 2). The gene discussed is MTOR; the disease is fibrosarcoma.