title: Molecular Testing for Gastrointestinal Cancer.
abstract: With recent advances in molecular diagnostic methods and targeted cancer therapies, several molecular tests have been recommended for gastric cancer (GC) and colorectal cancer (CRC). Microsatellite instability analysis of gastrointestinal cancers is performed to screen for Lynch syndrome, predict favorable prognosis, and screen patients for immunotherapy. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor has been approved in metastatic CRCs with wildtypeRAS(KRASandNRASexon 2-4). ABRAFmutation is required for predicting poor prognosis. Additionally, amplification of human epidermal growth factor receptor 2 (HER2) andMETis also associated with resistance to EGFR inhibitor in metastatic CRC patients. TheBRAFV600E mutation is found in sporadic microsatellite unstable CRCs, and thus is helpful for ruling out Lynch syndrome. In addition, theKRASmutation is a prognostic biomarker and thePIK3CAmutation is a molecular biomarker predicting response to phosphoinositide 3-kinase/AKT/mammalian target of rapamycin inhibitors and response to aspirin therapy in CRC patients. Additionally, HER2 testing should be performed in all recurrent or metastatic GCs. If the results of HER2 immunohistochemistry are equivocal,HER2silver or fluorescencein situhybridization testing are essential for confirmative determination of HER2 status. Epstein-Barr virus-positive GCs have distinct characteristics, including heavy lymphoid stroma, hypermethylation phenotype, and high expression of immune modulators. Recent advances in next-generation sequencing technologies enable us to examine various genetic alterations using a single test. Pathologists play a crucial role in ensuring reliable molecular testing and they should also take an integral role between molecular laboratories and clinicians.
authors.affiliation: Department of Pathology, Seoul National University Bundang Hospital, Seongnam, Korea.|Department of Pathology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Hye Seung
authors.initials: HS
authors.lastname: Lee
authors.affiliation: Department of Pathology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Woo Ho
authors.initials: WH
authors.lastname: Kim
authors.affiliation: Department of Pathology, Seoul National University Bundang Hospital, Seongnam, Korea.|Department of Pathology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Yoonjin
authors.initials: Y
authors.lastname: Kwak
authors.affiliation: Department of Pathology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jiwon
authors.initials: J
authors.lastname: Koh
authors.affiliation: Department of Pathology, SMG-SNU Boramae Medical Center, Seoul, Korea.
authors.forename: Jeong Mo
authors.initials: JM
authors.lastname: Bae
authors.affiliation: Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Kyoung-Mee
authors.initials: KM
authors.lastname: Kim
authors.affiliation: Department of Pathology, Seoul National University College of Medicine, Seoul, Korea.|Department of Pathology, SMG-SNU Boramae Medical Center, Seoul, Korea.
authors.forename: Mee Soo
authors.initials: MS
authors.lastname: Chang
authors.affiliation: Department of Pathology, Konkuk University School of Medicine, Seoul, Korea.
authors.forename: Hye Seung
authors.initials: HS
authors.lastname: Han
authors.affiliation: Department of Pathology, Inha University School of Medicine, Incheon, Korea.
authors.forename: Joon Mee
authors.initials: JM
authors.lastname: Kim
authors.affiliation: Department of Pathology, Seegene Medical Foundation, Busan, Korea.
authors.forename: Hwal Woong
authors.initials: HW
authors.lastname: Kim
authors.affiliation: Department of Pathology, Kosin University Gospel Hospital, Kosin University College of Medicine, Busan, Korea.
authors.forename: Hee Kyung
authors.initials: HK
authors.lastname: Chang
authors.affiliation: Department of Pathology, Hallym University Dongtan Sacred Heart Hospital, Hwaseong, Korea.
authors.forename: Young Hee
authors.initials: YH
authors.lastname: Choi
authors.affiliation: Department of Pathology, Catholic University of Daegu School of Medicine, Daegu, Korea.
authors.forename: Ji Y
authors.initials: JY
authors.lastname: Park
authors.affiliation: Department of Pathology, Yeungnam University College of Medicine, Daegu, Korea.
authors.forename: Mi Jin
authors.initials: MJ
authors.lastname: Gu
authors.affiliation: Department of Pathology, Seoul Red Cross Hospital, Seoul, Korea.
authors.forename: Min Jin
authors.initials: MJ
authors.lastname: Lhee
authors.affiliation: Department of Pathology, Inje University Sanggye Paik Hospital, Seoul, Korea.
authors.forename: Jung Yeon
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Pathology, Chung-Ang University College of Medicine, Seoul, Korea.
authors.forename: Hee Sung
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Department of Pathology, Wonju Severance Christian Hospital, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: Mee-Yon
authors.initials: MY
authors.lastname: Cho
keywords: Colorectal neoplasms; Gastric neoplasms; Molecular diagnosis; Prognosis; Targeted therapy