Roles of pathologists in molecular targeted cancer therapy

•  Introduction •  What is molecular targeted cancer therapy (MTCT)? •  Molecular targeted cancer therapy and target molecules •  Detection of target molecules and therapeutic response –  EGFR2 (HER2) –  EGFR (EGFR1) –  c‐kit (CD117) –  Bcr/abl –  AKT/mTOR –  Somatostatin receptors•  Roles of pathologists in molecular targeted cancer therapy •  SummaryMolecular targeted cancer therapy (MTCT) is the “personalized” or “individualized” approaches toward cancer which targets the particular molecular or genetic changes, i.e. over‐expression of molecules, and genetic amplification, mutations and translocations. MTCT is generally composed of two mechanisms, (1) humanized monoclonal antibodies (hMAB) and (2) tyrosine kinase inhibitors (TKI). Somatostatin analogue (SA) is the unique situation for the therapy of neuroendocrine tumors (NETs) which possess somatostatin receptor (SSTR). The cancers which are benefited by MTCT have been increased and will be increased to cover wide varieties of cancers. Good examples are (1) trastuzumab, hMAB against HER2 in breast cancers with HER2 over‐expression and amplification, (2) imatinib, TKI, for gastrointestinal stromal tumors (GISTs) with c‐kit mutation, (3) gefitinib, TKI, for lung adenocarcinoma with EGFR mutation. The drug effects have been reported to be associated with these molecular and genetic changes. It should be particularly emphasized to treat the patients with corresponding targeted molecular changes. These molecular and genetic analysis should be performed! On the right areas of the cancers, ample amount of viable cancer cells, where the major roles of pathologists are lied. This introductory review of MTCT describes more details of each MTCT.