Molecular Pathology of Gastroesophageal Tumors

Elucidation of molecular underpinnings in gastroesophageal neoplasms has expanded rapidly in the past decade. Upper gastrointestinal tract carcinomas can be characterized based on characteristic molecular classifications, and targeted therapy can be offered based on the results of immunohistochemistry for PD-L1, HER2, and mismatch repair proteins. Precursor neoplasms also demonstrate typical genetic findings. Gastrointestinal stromal tumors usually harbor KIT or PDGFRA mutations, but nearly all cases can now be ascribed to a particular molecular subtype. Additionally, specific mutations have implications for therapy selection and patient prognosis. Rare mesenchymal neoplasms, such as gastrointestinal neuroectodermal tumor and plexiform fibromyxoma, show characteristic translocations. Finally, numerous genetic syndromes associated with germline mutations predispose to upper gastrointestinal tract neoplasia.